Upgrade pytest version

[epassaro]

Description

• Unpinned pytest from tardis_env3.yml.
• Installing pytest-azurepiepelines from PyPI instead of GitHub.
• Using non boolean skip condition in integration test.
• Using pytestconfig instead of pytest.config.

Motivation and Context

@jaladh-singhal reported tests stopped working on Azure. Maybe it's time to move to pytest 5.

pytest.config is deprecated (see links below). Instead we are using pytestconfig and non-boolean skip conditions. Maybe we can switch to the recommended request fixture in a future PR.

See also:

• https://docs.pytest.org/en/latest/deprecations.html#pytest-config-global
• https://docs.pytest.org/en/latest/historical-notes.html
• https://docs.pytest.org/en/stable/reference.html#pytestconfig
• https://docs.pytest.org/en/latest/example/simple.html
• Cannot import xarray.tests due to use of pytest.config pydata/xarray#1353
• skipif documentation has broken example using pytest.config pytest-dev/pytest#472

How Has This Been Tested?

All tests passes on Azure.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have assigned/requested two reviewers for this pull request.

[codecov]

Codecov Report

Merging #1185 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1185   +/-   ##
=======================================
  Coverage   77.13%   77.13%           
=======================================
  Files          89       89           
  Lines        5551     5551           
=======================================
  Hits         4282     4282           
  Misses       1269     1269           

Impacted Files	Coverage Δ
tardis/montecarlo/tests/test_packet_source.py	86.36% <100.00%> (ø)
tardis/plasma/tests/test_complete_plasmas.py	97.77% <100.00%> (ø)
tardis/tests/integration_tests/test_integration.py	26.58% <100.00%> (ø)

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[jaladh-singhal]

Looks good to me! Thanks @epassaro for fixing this.

[wkerzendorf]

please pin this.