Change directory in pip-compile-docs tox session

tox.ini

@@ -52,8 +52,9 @@ skip_install = true
 
 [testenv:pip-compile-docs]
 description = compile requirements for the documentation
+changedir = {[testenv:build-docs]changedir}
 commands_pre =
-commands = python -m piptools compile --strip-extras --allow-unsafe --quiet docs/requirements.in {posargs}
+commands = python -m piptools compile --strip-extras --allow-unsafe --quiet requirements.in {posargs}
 
 [testenv:build-docs]
 description = build the documentation