use six.string_types instead of str to handle unicode in Python2

pipenv/utils.py

@@ -5,6 +5,7 @@ import tempfile
 import parse
 import requests
 import requirements
+import six
 
 try:
     from HTMLParser import HTMLParser
@@ -81,7 +82,7 @@ def convert_deps_to_pip(deps, r=True):
     for dep in deps.keys():
 
         # Default (e.g. '>1.10').
-        extra = deps[dep] if isinstance(deps[dep], str) else ''
+        extra = deps[dep] if isinstance(deps[dep], six.string_types) else ''
         version = ''
 
         # Get rid of '*'.

tests/test_utils.py

@@ -56,6 +56,11 @@ class TestUtils:
         deps = pipenv.utils.convert_deps_to_pip(deps, r=False)
         assert deps[0] == 'FooProject==1.2 --hash=sha256:2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824'
 
+        # test unicode values
+        deps = {u'django': u'==1.10'}
+        deps = pipenv.utils.convert_deps_to_pip(deps, r=False)
+        assert deps[0] == 'django>1.10'
+
 
     def test_convert_from_pip(self):