Make Wheel respect --root

pip/locations.py

@@ -127,7 +127,7 @@ else:
         default_log_file = os.path.join(user_dir, 'Library/Logs/pip.log')
 
 
-def distutils_scheme(dist_name, user=False, home=None):
+def distutils_scheme(dist_name, user=False, home=None, root=None):
     """
     Return a distutils install scheme
     """
@@ -141,6 +141,7 @@ def distutils_scheme(dist_name, user=False, home=None):
     # ideally, we'd prefer a scheme class that has no side-effects.
     i.user = user or i.user
     i.home = home or i.home
+    i.root = root or i.root
     i.finalize_options()
     for key in SCHEME_KEYS:
         scheme[key] = getattr(i, 'install_'+key)

pip/req.py

@@ -612,7 +612,7 @@ exec(compile(open(__file__).read().replace('\\r\\n', '\\n'), __file__, 'exec'))
             self.install_editable(install_options, global_options)
             return
         if self.is_wheel:
-            self.move_wheel_files(self.source_dir)
+            self.move_wheel_files(self.source_dir, root=root)
             self.install_succeeded = True
             return
 
@@ -831,8 +831,13 @@ exec(compile(open(__file__).read().replace('\\r\\n', '\\n'), __file__, 'exec'))
         self._bundle_build_dirs = bundle_build_dirs
         self._bundle_editable_dirs = bundle_editable_dirs
 
-    def move_wheel_files(self, wheeldir):
-        move_wheel_files(self.name, self.req, wheeldir, user=self.use_user_site, home=self.target_dir)
+    def move_wheel_files(self, wheeldir, root=None):
+        move_wheel_files(
+            self.name, self.req, wheeldir,
+            user=self.use_user_site,
+            home=self.target_dir,
+            root=root,
+        )
 
     @property
     def delete_marker_filename(self):

pip/wheel.py

@@ -103,10 +103,10 @@ def root_is_purelib(name, wheeldir):
                         return True
     return False
 
-def move_wheel_files(name, req, wheeldir, user=False, home=None):
+def move_wheel_files(name, req, wheeldir, user=False, home=None, root=None):
     """Install a wheel"""
 
-    scheme = distutils_scheme(name, user=user, home=home)
+    scheme = distutils_scheme(name, user=user, home=home, root=root)
 
     if root_is_purelib(name, wheeldir):
         lib_dir = scheme['purelib']