Add workaround for issue with pip 19.1, fixes #54

Author: gahjelle

tox.ini

@@ -6,6 +6,11 @@ skip_missing_interpreters = True
 
 
 [testenv]
+# Pin pip at version less than 19.1, see https://gitlab.com/python-devs/importlib_metadata/issues/54 for background
+# Full discussion at https://discuss.python.org/t/pip-19-1-and-installing-in-editable-mode-with-pyproject-toml/1553
+# One liner copied from https://github.com/ansible/molecule/pull/2009/files
+install_command =
+    python -c 'import subprocess, sys; pip_inst_cmd = sys.executable, "-m", "pip", "install"; subprocess.check_call(pip_inst_cmd + ("pip<19.1", )); subprocess.check_call(pip_inst_cmd + tuple(sys.argv[1:]))' {opts} {packages}
 commands =
     nocov: python -m unittest discover
     cov,diffcov: python -m coverage run {[coverage]rc} -m unittest discover {posargs}