Replace more six

src/pip/_internal/pyproject.py

@@ -4,7 +4,7 @@
 import os
 from collections import namedtuple
 
-from pip._vendor import six, toml
+from pip._vendor import toml
 from pip._vendor.packaging.requirements import InvalidRequirement, Requirement
 
 from pip._internal.exceptions import InstallationError
@@ -18,7 +18,7 @@ def _is_list_of_str(obj):
     # type: (Any) -> bool
     return (
         isinstance(obj, list) and
-        all(isinstance(item, six.string_types) for item in obj)
+        all(isinstance(item, str) for item in obj)
     )
 
 

src/pip/_internal/req/req_install.py

@@ -223,7 +223,7 @@ def __str__(self):
         if self.satisfied_by is not None:
             s += ' in {}'.format(display_path(self.satisfied_by.location))
         if self.comes_from:
-            if isinstance(self.comes_from, six.string_types):
+            if isinstance(self.comes_from, str):
                 comes_from = self.comes_from  # type: Optional[str]
             else:
                 comes_from = self.comes_from.from_path()
@@ -334,7 +334,7 @@ def from_path(self):
             return None
         s = str(self.req)
         if self.comes_from:
-            if isinstance(self.comes_from, six.string_types):
+            if isinstance(self.comes_from, str):
                 comes_from = self.comes_from
             else:
                 comes_from = self.comes_from.from_path()

tests/lib/venv.py

@@ -4,15 +4,12 @@
 import shutil
 import sys
 import textwrap
+import venv as _venv
 
-import six
 import virtualenv as _virtualenv
 
 from .path import Path
 
-if six.PY3:
-    import venv as _venv
-
 
 class VirtualEnvironment(object):
     """
@@ -37,8 +34,7 @@ def _update_paths(self):
         self.site = Path(lib) / 'site-packages'
         # Workaround for https://github.com/pypa/virtualenv/issues/306
         if hasattr(sys, "pypy_version_info"):
-            version_fmt = '{0}' if six.PY3 else '{0}.{1}'
-            version_dir = version_fmt.format(*sys.version_info)
+            version_dir = '{0}'.format(*sys.version_info)
             self.lib = Path(home, 'lib-python', version_dir)
         else:
             self.lib = Path(lib)