Adapt for pip 10 changing location of main

This is really a special case hack. The only reason that I'm okay with importing from pip's internals here is because we're using pip to install pip and this is really the cleanest way to allow for the bootstrapping to work. Further, the script doesn't break any of pip's internal assumptions (like sole control of logging) so this is fine.

Author: pradyunsg

virtualenv.py

@@ -858,7 +858,10 @@ def space_path2url(p):
         import tempfile
         import os
 
-        import pip
+        try:
+            from pip._internal import main as _main
+        except ImportError:
+            from pip import main as _main
 
         cert_data = pkgutil.get_data("pip._vendor.requests", "cacert.pem")
         if cert_data is not None:
@@ -874,7 +877,7 @@ def space_path2url(p):
                 args += ["--cert", cert_file.name]
             args += sys.argv[1:]
 
-            sys.exit(pip.main(args))
+            sys.exit(_main(args))
         finally:
             if cert_file is not None:
                 os.remove(cert_file.name)