Comment 0 for bug 1796378

Problem statement:

When deploying a subordinate charm, it simply ignores a series explicitly being set in bundle (and machine of primary charm, as well). I have a locally stored bundle [1], and while deploying it, I'm getting a following error while trying to establish a relation:

ERROR cannot deploy bundle: cannot add relation between "nova-compute:neutron-plugin" and "neutron-openvswitch:neutron-plugin": cannot add relation "nova-compute:neutron-plugin neutron-openvswitch:neutron-plugin": principal and subordinate applications' series must match

It looks like Juju ignores an original series of primary charm and takes just first one from subordinate's metadata [2]; if I manually swap a "xenial" with "bionic" in metadata, redeploy a subordinate and try to establish relation - all is fine: [3] (also, if try to deploy Xenial machines - all is fine too, this reproduces on Bionic machines)

Expected behaviour:
Subordinate charm should take its series from primary machine series, or, at least, respect a bundle "series: ..." settings.

[1] https://paste.ubuntu.com/p/KR3Cyt8qn2/
[2] https://paste.ubuntu.com/p/KNzhrxVVNr/
[3] https://paste.ubuntu.com/p/G9tHKyqPzk/

Environment:
Juju macOS 2.4.3-mojave-amd64 (same on Ubuntu 2.4.3-bionic-amd64)
Controller: https://paste.ubuntu.com/p/vgrGVvgCTp/