pytest JUnit XML deprecation warning (before pytest 6.0)

[kimadeline]

Initially reported in #10658:

Running tests with pytests shows the PytestDeprecationWarning: The 'junit_family' default value will change to 'xunit2' in pytest 6.0. Add 'junit_family=xunit1' to your pytest.ini file to keep the current format in future versions of pytest and silence this warning.

We add the --junitxml=<path/to/a/temp/xml/file> argument to our pytest command, so we should handle this warning instead of the users.

[bschnurr]

try adding this to your commandline
-o junit_family=xunit1