Additional dependency version pins in test requirements.

test_requirements.txt

@@ -1,7 +1,23 @@
+appdirs==1.4.3
+atomicwrites==1.2.1
+attrs==18.2.0
 black==18.9b0
+Click==7.0
+coverage==4.5.1
+docopt==0.6.2
 flake8==3.5.0
 flexmock==0.10.2
+mccabe==0.6.1
+more-itertools==4.3.0
+pluggy==0.7.1
+py==1.6.0
+pycodestyle==2.3.1
+pyflakes==2.0.0
 pykwalify==1.7.0
-pytest==3.8.1
+pytest==3.8.2
 pytest-cov==2.6.0
+python-dateutil==2.7.3
+PyYAML==3.13
 ruamel.yaml>0.15.0,<0.16.0
+six==1.11.0
+toml==0.10.0