Add i18n to v1/shell.py

Help, print, and exception messages will now all be translated. I
did not find any logging messages.

Motivation for this change:
    1. A patch for shell.py recently added i18n, we should be
       consistent with the additions from v1.
    2. I noticed a patch on v1/shell.py that had reviewers suggesting
       to use i18n, instead of applying it to one message lets do it
       for the whole file.

Change-Id: Ifd1bf25020c5f180a074165e2634a105bcbd4ed8

releasenotes/notes/use-i18n-for-v1-shell.py-08209f5721f20a1f.yaml

@@ -0,0 +1,3 @@
+---
+other:
+  - Use i18n for v1/shell.py