enable pip conflict checker

Author: mr-c

setup.py

@@ -47,7 +47,7 @@
           'ruamel.yaml >= 0.12.4, < 0.12.5',
           'rdflib >= 4.2.0, < 4.3.0',
           'shellescape >= 3.4.1, < 3.5',
-          'schema-salad >= 2.1.20161216210732, < 3',
+          'schema-salad >= 2.1.20161221160224, < 3',
           'typing >= 3.5.2, < 3.6',
           'cwltest >= 1.0.20160907111242',
           'pathlib2 >= 2.1.0'

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 #envlist = py35-lint,py34-lint,py33-lint,py27-lint,py35-unit,py34-unit,py33-unit,py27-unit
-envlist = py27-lint, py27-unit, py35-mypy
+envlist = py27-lint, py27-unit, pip27-pipconflictchecker, py35-mypy
 skipsdist = True
 
 [tox:travis]
@@ -38,6 +38,11 @@ commands = flake8 cwltool setup.py
 whitelist_externals = flake8
 deps = flake8
 
+[testenv:py27-pipconflictchecker]
+commands = pipconflictchecker
+whitelist_externals = pipconflictchecker
+deps = pip-conflict-checker
+
 [testenv:py35-unit]
 commands = python setup.py test