short test summary: different formats for skip, xfail and xpass

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• Include a detailed description of the bug or suggestion
• pip list of the virtual environment you are using
• pytest and operating system versions
• Minimal example if possible

In the report printed by pytest -ra, skip, xfail and xpass messages are formatted slightly differently from one another.

Python 3.7 / Arch Linux

$ pip list
Package        Version
-------------- -------
atomicwrites   1.3.0  
attrs          19.1.0 
more-itertools 7.0.0  
pip            19.0.3 
pluggy         0.9.0  
py             1.8.0  
pytest         4.4.0  
setuptools     40.8.0 
six            1.12.0

$ cat test_foo.py
import pytest

@pytest.mark.skip(reason="world")
def test_skip(): assert False

@pytest.mark.xfail(reason="hello")
def test_hello(): pass

@pytest.mark.xfail(reason="world")
def test_world(): assert False

$ pytest -ra
===================================== test session starts ======================================
platform linux -- Python 3.7.3, pytest-4.4.0, py-1.8.0, pluggy-0.9.0
rootdir: /tmp/foo
collected 3 items                                                                              

test_foo.py sXx                                                                          [100%]
=================================== short test summary info ====================================
SKIPPED [1] test_foo.py:3: world
XFAIL test_foo.py::test_world
  world
XPASS test_foo.py::test_hello hello

======================= 1 skipped, 1 xfailed, 1 xpassed in 0.02 seconds ========================

Notice that the skip message is the only one to include the line number and the xfail message the only one to be prepended with a newline.

Reproduce the report with the test_foo.py example and run pytest -ra to inspect the short test summary. Compare the skip, xfail, and xpass output, then make their formatting consistent and verify the updated summary with the same example.