The charm-helpers project have re-licensed to Apache 2.0
inline with the agreed licensing approach to intefaces,
layers and charms generally.
Resync helpers to bring charmhelpers inline with charm
codebase.
Change-Id: I20f9ea0c108a2e3849c5f9cfa5a074550af0a12f
Xenial does not install python2 by default; ensure that python2
and minimal module dependencies are installed prior to trying
to execute any python2 based hooks.
Update amulet tests to drop shared-db relation for n-gateway.
This change also includes a resync of charm-helpers to pickup
new changes for systemd support.
Change-Id: Icef9679cd1d1c96e8aa87bcedcf9735a41af8d52
Closes-Bug: #1555422
Ryan Beisner