Pin edx-lint to keep the version stable

requirements/edx/testing.in

@@ -23,7 +23,7 @@ bok-choy                  # Framework for browser automation tests, based on sel
 cssselect                 # Used to extract HTML fragments via CSS selectors in 2 test cases and pyquery
 ddt                       # Run a test case multiple times with different input; used in many, many of our tests
 edx-i18n-tools>=0.4.6     # Commands for developers and translators to extract, compile and validate translations
-edx-lint                  # pylint extensions for Open edX repositories
+edx-lint==0.6.0           # pylint extensions for Open edX repositories
 pylint-plugin-utils==0.3  # required by edx-lint and pinned explicitly here because newer versions don't guarantee python 2 support.
                           # can be removed when we get to python 3
 factory_boy==2.8.1        # Library for creating test fixtures, used in many tests