Comment 1 for bug 2003232

we also saw this on charm-prometheus-openstack-exporter on bionic:

unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install pip requires Python '>=3.7' but the running Python is 3.6.9
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install Traceback (most recent call last):
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install File "/var/lib/juju/agents/unit-prometheus-openstack-exporter-0/charm/hooks/install", line 8, in <module>
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install basic.bootstrap_charm_deps()
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install File "lib/charms/layer/basic.py", line 202, in bootstrap_charm_deps
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install _update_if_newer(pip, pre_install_pkgs)
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install File "lib/charms/layer/basic.py", line 367, in _update_if_newer
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install pkg], env=_get_subprocess_env())
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install File "/usr/lib/python3.6/subprocess.py", line 311, in check_call
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install raise CalledProcessError(retcode, cmd)
unit-prometheus-openstack-exporter-0: 20:05:30 WARNING unit.prometheus-openstack-exporter/0.install subprocess.CalledProcessError: Command '['/var/lib/juju/agents