Test failure test_guiqwt_solvable

cc @wolfv

Seems this one is failing somewhat sporadically. From the logging output it appears to mix two llvmdev pins?

```
FAILED [100%]Adding in variants from internal_defaults
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/linux_64_numpy1.18python3.6.____cpython.yaml
Adding in variants from argument_variants
tmpztk4lp2p/linux-64
tmpztk4lp2p/noarch
pkgs/main/linux-64
pkgs/main/noarch
pkgs/r/linux-64
conda-forge/noarch
pkgs/r/noarch
conda-forge/linux-64
msys2/linux-64
msys2/noarch
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/linux_64_numpy1.18python3.7.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/linux_64_numpy1.18python3.8.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/linux_64_numpy1.19python3.9.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.18python3.6.____cpython.yaml
conda-forge/noarch Using cache
tmpztk4lp2p/osx-64
tmpztk4lp2p/noarch
pkgs/main/osx-64
pkgs/r/osx-64
pkgs/r/noarch
pkgs/main/noarch
conda-forge/osx-64
msys2/osx-64
msys2/noarch
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.18python3.7.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.18python3.8.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.19python3.9.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.18python3.6.____cpython.yaml
conda-forge/noarch Using cache
pkgs/main/noarch Using cache
pkgs/r/noarch Using cache
tmpztk4lp2p/win-64
tmpztk4lp2p/noarch
pkgs/r/win-64
pkgs/main/win-64
conda-forge/win-64
msys2/win-64
msys2/noarch
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.18python3.7.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.18python3.8.____cpython.yaml
Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.19python3.9.____cpython.yaml
{}
Cloning into 'repo'...
/Users/marius/mambaforge/envs/cf-scripts/lib/python3.8/site-packages/conda/_vendor/auxlib/_vendor/five.py:49: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
from imp import reload # noqa
Setting build platform. This is only useful when pretending to be on another platform, such as for rendering necessary dependencies on a non-native platform. I trust that you know what you're doing.
Setting build arch. This is only useful when pretending to be on another arch, such as for rendering necessary dependencies on a non-native arch. I trust that you know what you're doing.
No numpy version specified in conda_build_config.yaml. Falling back to default numpy value of 1.16
WARNING:conda_forge_tick.mamba_solver:downloading libcfgraph file index
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/noarch/sysroot_linux-64-2.12-he073ed8_14.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/linux-64/libgfortran5-11.2.0-h5c6108e_11.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/linux-64/libclang-11.1.0-default_ha53f305_1.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=6, misses=98, maxsize=10240, currsize=98)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 299 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/linux_64_numpy1.18python3.7.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/linux-64/icu-58.2-hf484d3e_1000.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://repo.anaconda.com/pkgs/main/linux-64/gstreamer-1.14.0-h28cd5cc_2.conda
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://repo.anaconda.com/pkgs/main/linux-64/gst-plugins-base-1.14.0-hbbd80ab_1.conda
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://repo.anaconda.com/pkgs/main/linux-64/qt-5.6.3-h8bf5577_3.conda
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/linux-64/pyqt-5.6.0-py37h13b7fb3_1008.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=75, misses=115, maxsize=10240, currsize=115)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 318 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/linux_64_numpy1.18python3.8.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=167, misses=128, maxsize=10240, currsize=128)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 313 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/linux_64_numpy1.19python3.9.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=258, misses=142, maxsize=10240, currsize=142)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 345 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.18python3.6.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/osx-64/libgfortran-5.0.0-9_3_0_h6c81a4c_23.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/osx-64/libclang-11.1.0-default_he082bbe_1.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=268, misses=218, maxsize=10240, currsize=218)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 493 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.18python3.7.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/osx-64/libclang-8.0.1-ha1b3eb9_2.tar.bz2
WARNING:conda_forge_tick.mamba_solver:MAMBA [osx-64] failed to solve specs

['icu >=64.2,<65.0a0',
'openjpeg >=2.4.0,<3.0a0',
'pillow',
'libopenblas >=0.3.18,<1.0a0',
'expat >=2.4.1,<3.0a0',
'lerc >=3.0,<4.0a0',
'python_abi 3.7.* *_cp37m',
'pyqt >=5.12.3,<5.13.0a0',
'numpy',
'libblas >=3.9.0,<4.0a0',
'qtpy >=1.3',
'readline >=8.1,<9.0a0',
'openssl >=3.0.0,<4.0a0',
'dbus >=1.13.6,<2.0a0',
'liblapack >=3.9.0,<3.10.0a0',
'sqlite >=3.36.0,<4.0a0',
'pythonqwt >=0.5.0',
'libpng >=1.6.37,<1.7.0a0',
'libtiff >=4.3.0,<5.0a0',
'libcxx >=11.1.0',
'libglib >=2.70.0,<3.0a0',
'lz4-c >=1.9.3,<1.10.0a0',
'libgfortran5 >=9.3.0',
'qt >=5.12.5,<5.13.0a0',
'ncurses >=6.2,<7.0a0',
'xz >=5.2.5,<6.0a0',
'libiconv >=1.16,<2.0a0',
'libdeflate >=1.8,<1.9.0a0',
'pyqt',
'guidata >=1.7.0',
'scipy >=0.7',
'gettext >=0.19.8.1,<1.0a0',
'lcms2 >=2.12,<3.0a0',
'nspr >=4.30,<5.0a0',
'libcblas >=3.9.0,<4.0a0',
'pcre >=8.45,<9.0a0',
'python >=3.7,<3.8.0a0',
'libwebp-base',
'libzlib >=1.2.11,<1.3.0a0',
'libffi >=3.4,<4.0a0',
'jpeg >=9d,<10a',
'tk >=8.6.11,<8.7.0a0',
'nss >=3.69,<4.0a0',
'libllvm8 8.0.1.* 0',
'freetype >=2.10.4,<3.0a0',
'zstd >=1.5.0,<1.6.0a0']

for channels

['file:///var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/tmpztk4lp2p',
'conda-forge',
'defaults',
'msys2']

The reported errors are:

Encountered problems while solving:
- nothing provides requested libllvm8 8.0.1.* 0

WARNING:conda_forge_tick.mamba_solver:MAMBA [osx-64] failed to solve specs

['pip',
'icu >=64.2,<65.0a0',
'openjpeg >=2.4.0,<3.0a0',
'pillow',
'libopenblas >=0.3.18,<1.0a0',
'expat >=2.4.1,<3.0a0',
'lerc >=3.0,<4.0a0',
'python_abi 3.7.* *_cp37m',
'pyqt >=5.12.3,<5.13.0a0',
'numpy',
'libblas >=3.9.0,<4.0a0',
'qtpy >=1.3',
'readline >=8.1,<9.0a0',
'openssl >=3.0.0,<4.0a0',
'dbus >=1.13.6,<2.0a0',
'liblapack >=3.9.0,<3.10.0a0',
'sqlite >=3.36.0,<4.0a0',
'pythonqwt >=0.5.0',
'libpng >=1.6.37,<1.7.0a0',
'libtiff >=4.3.0,<5.0a0',
'libcxx >=11.1.0',
'libglib >=2.70.0,<3.0a0',
'lz4-c >=1.9.3,<1.10.0a0',
'libgfortran5 >=9.3.0',
'qt >=5.12.5,<5.13.0a0',
'ncurses >=6.2,<7.0a0',
'xz >=5.2.5,<6.0a0',
'libiconv >=1.16,<2.0a0',
'libdeflate >=1.8,<1.9.0a0',
'pyqt',
'guidata >=1.7.0',
'scipy >=0.7',
'gettext >=0.19.8.1,<1.0a0',
'lcms2 >=2.12,<3.0a0',
'nspr >=4.30,<5.0a0',
'libcblas >=3.9.0,<4.0a0',
'pcre >=8.45,<9.0a0',
'python >=3.7,<3.8.0a0',
'libwebp-base',
'libzlib >=1.2.11,<1.3.0a0',
'libffi >=3.4,<4.0a0',
'jpeg >=9d,<10a',
'tk >=8.6.11,<8.7.0a0',
'nss >=3.69,<4.0a0',
'libllvm8 8.0.1.* 0',
'freetype >=2.10.4,<3.0a0',
'zstd >=1.5.0,<1.6.0a0']

for channels

['file:///var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/tmpztk4lp2p',
'conda-forge',
'defaults',
'msys2']

The reported errors are:

Encountered problems while solving:
- nothing provides requested libllvm8 8.0.1.* 0

INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=331, misses=232, maxsize=10240, currsize=232)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 552 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.18python3.8.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=404, misses=245, maxsize=10240, currsize=245)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 630 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.19python3.9.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://repo.anaconda.com/pkgs/main/osx-64/pyqt-5.9.2-py39h23ab428_6.conda
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=460, misses=255, maxsize=10240, currsize=255)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 701 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.18python3.6.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/win-64/libclang-11.1.0-default_h5c34c98_1.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=466, misses=306, maxsize=10240, currsize=306)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 542 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.18python3.7.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=510, misses=319, maxsize=10240, currsize=319)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 550 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.18python3.8.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=554, misses=332, maxsize=10240, currsize=332)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 563 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/win_64_numpy1.19python3.9.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=599, misses=345, maxsize=10240, currsize=345)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 574 MB

tests/test_mamba_solvable.py:278 (test_guiqwt_solvable)
tmp_path = PosixPath('/private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0')

def test_guiqwt_solvable(tmp_path):
"""test for run exports as a single string in pyqt"""
feedstock_dir = clone_and_checkout_repo(
tmp_path,
"https://github.com/conda-forge/guiqwt-feedstock",
ref="master",
)
solvable, errors, solvable_by_variant = is_recipe_solvable(feedstock_dir)
pprint.pprint(solvable_by_variant)
> assert solvable
E assert False

test_mamba_solvable.py:288: AssertionError
```

Notably this feels off?

```
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/osx-64/libclang-11.1.0-default_he082bbe_1.tar.bz2
INFO:conda_forge_tick.mamba_solver:RUN EXPORT cache status: CacheInfo(hits=268, misses=218, maxsize=10240, currsize=218)
INFO:conda_forge_tick.mamba_solver:MAMBA SOLVER MEM USAGE: 493 MB
INFO:conda_build.variants:Adding in variants from /private/var/folders/wp/0dbcjg8n2y95z6_3_5khb9kr0000gn/T/pytest-of-marius/pytest-8/test_guiqwt_solvable0/repo/.ci_support/osx_64_numpy1.18python3.7.____cpython.yaml
INFO:conda_forge_tick.mamba_solver:RUN EXPORTS: downloading package https://conda.anaconda.org/conda-forge/osx-64/libclang-8.0.1-ha1b3eb9_2.tar.bz2
```