Explicity allow env in tox configuration.

Author: matthewwardrop

tox.ini

@@ -26,6 +26,8 @@ setenv=
   OMP_NUM_THREADS=1
   MKL_NUM_THREADS=1
   VML_NUM_THREADS=1
+allowlist_externals=
+  env
 commands=
   pytest -vv --cov=patsy --cov-config={toxinidir}/.coveragerc --cov-report=term-missing --cov-report=xml --cov-report=html:{toxworkdir}/coverage/{envname} {posargs:}
   env PATSY_AVOID_OPTIONAL_DEPENDENCIES=1 pytest -vv --cov=patsy --cov-config={toxinidir}/.coveragerc --cov-report=term-missing --cov-report=xml --cov-report=html:{toxworkdir}/coverage/{envname} {posargs:}