* charm-helpers sync for classic charms
* build.lock file for reactive charms
* ensure tox.ini is from release-tools
* ensure requirements.txt files are from release-tools
* On reactive charms:
- ensure stable/21.04 branch for charms.openstack
- ensure stable/21.04 branch for charm-helpers
* Manual fix to build.lock to work around bug [1]
[1] https://github.com/juju/charm-tools/issues/603
Change-Id: I6be25d404436647a19e18231ccd0985dd49bb858
46797fc986