Merge pull request #4775 from jmchilton/pin_pydocstyle

[17.09] Pin pydocstyles for stable release.

tox.ini

@@ -8,6 +8,7 @@ whitelist_externals = bash
 deps =
     flake8==3.4.1
     flake8-docstrings==1.1.0
+    pydocstyle==2.0.0
 
 [testenv:py33-lint]
 commands = bash .ci/flake8_py3_wrapper.sh
@@ -81,7 +82,7 @@ skip_install = True
 deps =
     flake8
     flake8-docstrings==1.1.0
-
+    pydocstyle==2.0.0
 
 [testenv:py27-lint-docstring-include-list]
 commands = bash .ci/flake8_wrapper_docstrings.sh --include
@@ -90,3 +91,4 @@ skip_install = True
 deps =
     flake8==3.4.1
     flake8-docstrings==1.1.0
+    pydocstyle==2.0.0