Shellquote paths to requirements files

- Allows for windows paths with spaces in them
- Fixes #2054

Signed-off-by: Dan Ryan <dan@danryan.co>

HISTORY.txt

@@ -10,6 +10,7 @@
  - Remove GPL'ed code.
  - Make imports lazy to improve initial load time.
  - Extra path searching for python at runtime.
+ - Shellquote paths to requirement files in case of spaces on windows.
  - Require `--python` values to exist when passing a path.
  - Bugfix for environment variable expansion in 'unlocked' pipfiles.
  - Bugfix for `--deploy` flag.

pipenv/core.py

@@ -1476,7 +1476,7 @@ def pip_install(
     if package_name.startswith('-e '):
         install_reqs = ' -e "{0}"'.format(package_name.split('-e ')[1])
     elif r:
-        install_reqs = ' -r {0}'.format(r)
+        install_reqs = ' -r {0}'.format(escape_grouped_arguments(r))
     else:
         install_reqs = ' "{0}"'.format(package_name)
     # Skip hash-checking mode, when appropriate.