Install eval dependencies with --user & ensure user base var is set

Due to the way that `find` executes -exec arguments we need to
run the pip install's inside another `sh` instance so that the
PYTHONUSERBASE environment variable is correctly picked up.

Additionally, we need to specify `--user` so that pip respects
the PYTHONUSERBASE variable at all.

Author: jb3

deployment.yaml

@@ -31,8 +31,8 @@ spec:
                   - "-c"
                   - >-
                     find /lang/python -mindepth 1 -maxdepth 1 -type d -exec
-                    PYTHONUSERBASE=/snekbox/user_base &&
-                    {}/bin/python -m pip install -U
+                    sh -c 'PYTHONUSERBASE=/snekbox/user_base &&
+                    {}/bin/python -m pip install --user -U
                     anyio[trio]~=3.6
                     arrow~=1.2
                     attrs~=22.2
@@ -56,7 +56,7 @@ spec:
                     typing-extensions~=4.4
                     tzdata~=2022.7
                     yarl~=1.8
-                    \;
+                    ' \;
       volumes:
         - name: snekbox-user-base-volume
           hostPath: