Remove pip uninstall temporary directories

Pip leaves behind directories with names starting with `~` in the
site-packages directory due to a bug that occurs when uninstalling
packages from an NFS filesystem.

See pypa/pip#6327.

Fixes #206.

.gitlab-ci.yml

@@ -313,6 +313,10 @@ release:
       set -e
       pip install --upgrade pipenv pip setuptools
       pipenv install --system --deploy
+      # FIXME: remove pip uninstall temporary directories left behind due to
+      # bug with pip on NFS. See https://github.com/pypa/pip/issues/6327
+      chmod -R ug+rwx .local/lib/python3.6/site-packages/~*
+      rm -rf .local/lib/python3.6/site-packages/~*
       gwcelery condor resubmit
       EOF