Remove old .pyc files

Avoid Byte code errors: bad magic number in 'ceph': b'\x03\xf3\r\n'

Change-Id: I156803991b2b3783ef633837a3945f50a86ef0dc
Closes-Bug: #1825392

hooks/upgrade-charm

@@ -1,4 +1,9 @@
 #!/bin/bash -e
-# Re-install dependencies to deal with py2->py3 switch for charm
 
+# Wrapper to ensure that old python bytecode isn't hanging around
+# after we upgrade the charm with newer libraries
+find . -iname '*.pyc' -delete
+find . -name '__pycache__' -prune -exec rm -rf "{}" \;
+
+# Re-install dependencies to deal with py2->py3 switch for charm
 ./hooks/install_deps