Workaround for editable installs with pip 19.1 (#5168)

Workaround for editable installs with pip 19.1

tox.ini

@@ -73,7 +73,8 @@ commands = pre-commit run --all-files --show-diff-on-failure
 
 [testenv:docs]
 basepython = python3
-usedevelop = True
+# broken due to pip 19.1 (#5167)
+# usedevelop = True
 changedir = doc/en
 deps = -r{toxinidir}/doc/en/requirements.txt
 
@@ -127,7 +128,8 @@ commands =
 [testenv:release]
 decription = do a release, required posarg of the version number
 basepython = python3.6
-usedevelop = True
+# broken due to pip 19.1 (#5167)
+# usedevelop = True
 passenv = *
 deps =
     colorama