Use vistir path normalization for shortened windows paths

Signed-off-by: Dan Ryan <dan.ryan@canonical.com>

pipenv/core.py

@@ -1469,7 +1469,7 @@ def pip_install(
     )
     pip_command.extend(pip_args)
     if r:
-        pip_command.extend(["-r", r])
+        pip_command.extend(["-r", vistir.path.normalize_path(r)])
     elif line:
         pip_command.extend(line)
     pip_command.extend(prepare_pip_source_args(sources))

tests/integration/test_project.py

@@ -8,8 +8,8 @@ import pytest
 
 from pipenv.patched import pipfile
 from pipenv.project import Project
-from pipenv.utils import temp_environ, normalize_path
-from pipenv.vendor.vistir.path import is_in_path
+from pipenv.utils import temp_environ
+from pipenv.vendor.vistir.path import is_in_path, normalize_path
 from pipenv.vendor.delegator import run as delegator_run