Testsuite failed during weekly CRON job run

ref : https://travis-ci.org/github/enthought/mayavi/builds/702500915

The failures are happening with VTK 8 + Python 3.6 on both MacOS and Linux variants. The test failures are :

```
======================================================================

ERROR: Basic tests for the VTK module.

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_class_tree.py", line 88, in test_basic_vtk

self.assertEqual(names, expect)

UnboundLocalError: local variable 'expect' referenced before assignment

======================================================================

ERROR: Test ContextDevice2D Get/SetMatrix API

----------------------------------------------------------------------

Traceback (most recent call last):

File "tvtk_classes/tvtk_helper.py", line 23, in get_module

globals(), locals(), [fname])

ModuleNotFoundError: No module named 'tvtk.custom.bezier_triangle'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 823, in test_contextdevice2d_matrix_api

if has_subclass(klass):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 68, in has_subclass

return bool(inspect.getmembers(tvtk, is_sub_class))

File "/home/travis/.edm/envs/edm/lib/python3.6/inspect.py", line 342, in getmembers

value = getattr(object, key)

File "tvtk_classes/tvtk_helper.py", line 1767, in

BezierTriangle = property(lambda self: get_class('BezierTriangle'))

File "tvtk_classes/tvtk_helper.py", line 47, in get_class

mod = get_module(fname)

File "tvtk_classes/tvtk_helper.py", line 28, in get_module

mod = __import__('tvtk.tvtk_classes.%s'%fname, globals(), locals(), [fname])

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/bezier_triangle.py", line 29, in

from tvtk.tvtk_classes.higher_order_triangle import HigherOrderTriangle

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/higher_order_triangle.py", line 32, in

class HigherOrderTriangle(NonLinearCell):

File "tvtk_classes/higher_order_triangle.py", line 56, in HigherOrderTriangle

parametric_coords = traits.Array(enter_set=True, auto_set=False, shape=(9,), dtype="float", value=(nan, nan, 0.0, 6.91176469033213e-310, 2.37e-322, 2.93e-321, 0.0, 2.20347903e-316, nan), cols=3, desc=\

NameError: name 'nan' is not defined

======================================================================

ERROR: Test if VTK object changes when trait is changed.

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 181, in test_do_change

self.assertEqual(val, getattr(p, t))

File "/home/travis/.edm/envs/edm/lib/python3.6/unittest/case.py", line 829, in assertEqual

assertion_func(first, second, msg=msg)

File "/home/travis/.edm/envs/edm/lib/python3.6/unittest/case.py", line 819, in _baseAssertEqual

if not first == second:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

======================================================================

ERROR: Test ObjectFactory Get/SetEnableFlag API

----------------------------------------------------------------------

Traceback (most recent call last):

File "tvtk_classes/tvtk_helper.py", line 23, in get_module

globals(), locals(), [fname])

ModuleNotFoundError: No module named 'tvtk.custom.bezier_triangle'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 803, in test_object_factory_enableflag_api

if has_subclass(klass):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 68, in has_subclass

return bool(inspect.getmembers(tvtk, is_sub_class))

File "/home/travis/.edm/envs/edm/lib/python3.6/inspect.py", line 342, in getmembers

value = getattr(object, key)

File "tvtk_classes/tvtk_helper.py", line 1767, in

BezierTriangle = property(lambda self: get_class('BezierTriangle'))

File "tvtk_classes/tvtk_helper.py", line 47, in get_class

mod = get_module(fname)

File "tvtk_classes/tvtk_helper.py", line 28, in get_module

mod = __import__('tvtk.tvtk_classes.%s'%fname, globals(), locals(), [fname])

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/bezier_triangle.py", line 29, in

from tvtk.tvtk_classes.higher_order_triangle import HigherOrderTriangle

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/higher_order_triangle.py", line 32, in

class HigherOrderTriangle(NonLinearCell):

File "tvtk_classes/higher_order_triangle.py", line 56, in HigherOrderTriangle

parametric_coords = traits.Array(enter_set=True, auto_set=False, shape=(9,), dtype="float", value=(nan, nan, 0.0, 6.91176469033213e-310, 2.37e-322, 2.93e-321, 0.0, 2.20347903e-316, nan), cols=3, desc=\

NameError: name 'nan' is not defined

======================================================================

ERROR: Test if all the TVTK classes can be instantiated

----------------------------------------------------------------------

Traceback (most recent call last):

File "tvtk_classes/tvtk_helper.py", line 23, in get_module

globals(), locals(), [fname])

ModuleNotFoundError: No module named 'tvtk.custom.bezier_triangle'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 913, in setUp

tvtk_klass = getattr(tvtk, tvtk_klass_name, None)

File "tvtk_classes/tvtk_helper.py", line 1767, in

BezierTriangle = property(lambda self: get_class('BezierTriangle'))

File "tvtk_classes/tvtk_helper.py", line 47, in get_class

mod = get_module(fname)

File "tvtk_classes/tvtk_helper.py", line 28, in get_module

mod = __import__('tvtk.tvtk_classes.%s'%fname, globals(), locals(), [fname])

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/bezier_triangle.py", line 29, in

from tvtk.tvtk_classes.higher_order_triangle import HigherOrderTriangle

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/higher_order_triangle.py", line 32, in

class HigherOrderTriangle(NonLinearCell):

File "tvtk_classes/higher_order_triangle.py", line 56, in HigherOrderTriangle

parametric_coords = traits.Array(enter_set=True, auto_set=False, shape=(9,), dtype="float", value=(nan, nan, 0.0, 6.91176469033213e-310, 2.37e-322, 2.93e-321, 0.0, 2.20347903e-316, nan), cols=3, desc=\

NameError: name 'nan' is not defined

======================================================================

ERROR: Test if all of the traits can be obtained

----------------------------------------------------------------------

Traceback (most recent call last):

File "tvtk_classes/tvtk_helper.py", line 23, in get_module

globals(), locals(), [fname])

ModuleNotFoundError: No module named 'tvtk.custom.bezier_triangle'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 913, in setUp

tvtk_klass = getattr(tvtk, tvtk_klass_name, None)

File "tvtk_classes/tvtk_helper.py", line 1767, in

BezierTriangle = property(lambda self: get_class('BezierTriangle'))

File "tvtk_classes/tvtk_helper.py", line 47, in get_class

mod = get_module(fname)

File "tvtk_classes/tvtk_helper.py", line 28, in get_module

mod = __import__('tvtk.tvtk_classes.%s'%fname, globals(), locals(), [fname])

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/bezier_triangle.py", line 29, in

from tvtk.tvtk_classes.higher_order_triangle import HigherOrderTriangle

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/higher_order_triangle.py", line 32, in

class HigherOrderTriangle(NonLinearCell):

File "tvtk_classes/higher_order_triangle.py", line 56, in HigherOrderTriangle

parametric_coords = traits.Array(enter_set=True, auto_set=False, shape=(9,), dtype="float", value=(nan, nan, 0.0, 6.91176469033213e-310, 2.37e-322, 2.93e-321, 0.0, 2.20347903e-316, nan), cols=3, desc=\

NameError: name 'nan' is not defined

======================================================================

ERROR: test_import_tvtk_does_not_import_gui (tvtk.tests.test_tvtk.TestTVTKModule)

----------------------------------------------------------------------

Traceback (most recent call last):

File "tvtk_classes/tvtk_helper.py", line 23, in get_module

globals(), locals(), [fname])

ModuleNotFoundError: No module named 'tvtk.custom.bezier_triangle'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 913, in setUp

tvtk_klass = getattr(tvtk, tvtk_klass_name, None)

File "tvtk_classes/tvtk_helper.py", line 1767, in

BezierTriangle = property(lambda self: get_class('BezierTriangle'))

File "tvtk_classes/tvtk_helper.py", line 47, in get_class

mod = get_module(fname)

File "tvtk_classes/tvtk_helper.py", line 28, in get_module

mod = __import__('tvtk.tvtk_classes.%s'%fname, globals(), locals(), [fname])

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/bezier_triangle.py", line 29, in

from tvtk.tvtk_classes.higher_order_triangle import HigherOrderTriangle

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/higher_order_triangle.py", line 32, in

class HigherOrderTriangle(NonLinearCell):

File "tvtk_classes/higher_order_triangle.py", line 56, in HigherOrderTriangle

parametric_coords = traits.Array(enter_set=True, auto_set=False, shape=(9,), dtype="float", value=(nan, nan, 0.0, 6.91176469033213e-310, 2.37e-322, 2.93e-321, 0.0, 2.20347903e-316, nan), cols=3, desc=\

NameError: name 'nan' is not defined

======================================================================

ERROR: Test if none of the TVTK classes' traits has a value of "*_p_void"

----------------------------------------------------------------------

Traceback (most recent call last):

File "tvtk_classes/tvtk_helper.py", line 23, in get_module

globals(), locals(), [fname])

ModuleNotFoundError: No module named 'tvtk.custom.bezier_triangle'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 913, in setUp

tvtk_klass = getattr(tvtk, tvtk_klass_name, None)

File "tvtk_classes/tvtk_helper.py", line 1767, in

BezierTriangle = property(lambda self: get_class('BezierTriangle'))

File "tvtk_classes/tvtk_helper.py", line 47, in get_class

mod = get_module(fname)

File "tvtk_classes/tvtk_helper.py", line 28, in get_module

mod = __import__('tvtk.tvtk_classes.%s'%fname, globals(), locals(), [fname])

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/bezier_triangle.py", line 29, in

from tvtk.tvtk_classes.higher_order_triangle import HigherOrderTriangle

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/higher_order_triangle.py", line 32, in

class HigherOrderTriangle(NonLinearCell):

File "tvtk_classes/higher_order_triangle.py", line 56, in HigherOrderTriangle

parametric_coords = traits.Array(enter_set=True, auto_set=False, shape=(9,), dtype="float", value=(nan, nan, 0.0, 6.91176469033213e-310, 2.37e-322, 2.93e-321, 0.0, 2.20347903e-316, nan), cols=3, desc=\

NameError: name 'nan' is not defined

======================================================================

ERROR: Test if all the attributes with MinValue/MaxValue are traits

----------------------------------------------------------------------

Traceback (most recent call last):

File "tvtk_classes/tvtk_helper.py", line 23, in get_module

globals(), locals(), [fname])

ModuleNotFoundError: No module named 'tvtk.custom.bezier_triangle'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_tvtk.py", line 913, in setUp

tvtk_klass = getattr(tvtk, tvtk_klass_name, None)

File "tvtk_classes/tvtk_helper.py", line 1767, in

BezierTriangle = property(lambda self: get_class('BezierTriangle'))

File "tvtk_classes/tvtk_helper.py", line 47, in get_class

mod = get_module(fname)

File "tvtk_classes/tvtk_helper.py", line 28, in get_module

mod = __import__('tvtk.tvtk_classes.%s'%fname, globals(), locals(), [fname])

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/bezier_triangle.py", line 29, in

from tvtk.tvtk_classes.higher_order_triangle import HigherOrderTriangle

File "", line 971, in _find_and_load

File "", line 955, in _find_and_load_unlocked

File "", line 656, in _load_unlocked

File "", line 626, in _load_backward_compatible

File "tvtk_classes/higher_order_triangle.py", line 32, in

class HigherOrderTriangle(NonLinearCell):

File "tvtk_classes/higher_order_triangle.py", line 56, in HigherOrderTriangle

parametric_coords = traits.Array(enter_set=True, auto_set=False, shape=(9,), dtype="float", value=(nan, nan, 0.0, 6.91176469033213e-310, 2.37e-322, 2.93e-321, 0.0, 2.20347903e-316, nan), cols=3, desc=\

NameError: name 'nan' is not defined

======================================================================

FAIL: test_get_children (tvtk.tests.test_browser.TestFullTreeGenrator)

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_browser.py", line 112, in test_get_children

self.assertTrue(len(kids) in [6, 7])

AssertionError: False is not true

======================================================================

FAIL: test_box (tvtk.tests.test_visual.TestVisual)

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_visual.py", line 170, in test_box

assert_allclose(b.polydata.bounds, bounds)

File "/home/travis/.edm/envs/edm/lib/python3.6/site-packages/numpy/testing/_private/utils.py", line 1515, in assert_allclose

verbose=verbose, header=header, equal_nan=equal_nan)

File "/home/travis/.edm/envs/edm/lib/python3.6/site-packages/numpy/testing/_private/utils.py", line 841, in assert_array_compare

raise AssertionError(msg)

AssertionError:

Not equal to tolerance rtol=1e-07, atol=0

Mismatch: 66.7%

Max absolute difference: 0.20710678

Max relative difference: 0.29289322

x: array([-0.5, 0.5, -0.5, 0.5, -0.5, 0.5])

y: array([-0.707107, 0.707107, -0.707107, 0.707107, -0.5 , 0.5 ])

======================================================================

FAIL: test_helix (tvtk.tests.test_visual.TestVisual)

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_visual.py", line 258, in test_helix

assert_allclose(h.polydata.bounds, bounds, atol=3e-2, rtol=0)

File "/home/travis/.edm/envs/edm/lib/python3.6/site-packages/numpy/testing/_private/utils.py", line 1515, in assert_allclose

verbose=verbose, header=header, equal_nan=equal_nan)

File "/home/travis/.edm/envs/edm/lib/python3.6/site-packages/numpy/testing/_private/utils.py", line 841, in assert_array_compare

raise AssertionError(msg)

AssertionError:

Not equal to tolerance rtol=0, atol=0.03

Mismatch: 66.7%

Max absolute difference: 0.8097887

Max relative difference: 0.66666667

x: array([1.02 , 2. , 0.809789, 1.190211, 0.8 , 1.2 ])

y: array([0.8, 1.2, 1. , 2. , 0.8, 1.2])

======================================================================

FAIL: Check if parser is usable without the tree.

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_vtk_parser.py", line 272, in test_no_tree

self.test_parse()

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_vtk_parser.py", line 49, in test_parse

{'Debug': 0, 'GlobalWarningDisplay': 1})

AssertionError: {'Debug': False, 'GlobalWarningDisplay': 0} != {'Debug': 0, 'GlobalWarningDisplay': 1}

- {'Debug': False, 'GlobalWarningDisplay': 0}

? ^^^^^ ^

+ {'Debug': 0, 'GlobalWarningDisplay': 1}

? ^ ^

======================================================================

FAIL: Check if the methods are organized correctly.

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/build/enthought/mayavi/tvtk/tests/test_vtk_parser.py", line 49, in test_parse

{'Debug': 0, 'GlobalWarningDisplay': 1})

AssertionError: {'Debug': False, 'GlobalWarningDisplay': 0} != {'Debug': 0, 'GlobalWarningDisplay': 1}

- {'Debug': False, 'GlobalWarningDisplay': 0}

? ^^^^^ ^

+ {'Debug': 0, 'GlobalWarningDisplay': 1}

? ^ ^
```