From debug-log:

unit-prometheus2-0: 11:14:50 INFO juju.worker.uniter awaiting error resolution for "install" hook
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   error: subprocess-exited-with-error
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   × python setup.py egg_info did not run successfully.
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   │ exit code: 1
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   ╰─> [1 lines of output]
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install       error in Tempita setup command: use_2to3 is invalid.
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install       [end of output]
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   note: This error originates from a subprocess, and is likely not a problem with pip.
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install error: metadata-generation-failed
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install 
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install × Encountered error while generating package metadata.
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install ╰─> See above for output.
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install 
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install note: This is an issue with the package mentioned above, not pip.
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install hint: See above for details.
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install Traceback (most recent call last):
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   File "/var/lib/juju/agents/unit-prometheus2-0/charm/hooks/install", line 8, in <module>
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install     basic.bootstrap_charm_deps()
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   File "/var/lib/juju/agents/unit-prometheus2-0/charm/lib/charms/layer/basic.py", line 212, in bootstrap_charm_deps
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install     check_call([pip, 'install', '-U', reinstall_flag, '--no-index',
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install   File "/usr/lib/python3.10/subprocess.py", line 369, in check_call
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install     raise CalledProcessError(retcode, cmd)
unit-prometheus2-0: 11:14:59 WARNING unit.prometheus2/0.install subprocess.CalledProcessError: Command '['/var/lib/juju/agents/unit-prometheus2-0/.venv/bin/pip', 'install', '-U', '--force-reinstall', '--no-index', '--no-cache-dir', '-f', 'wheelhouse', 'Jinja2==2.10.1', 'chardet==3.0.4', 'requests==2.24.0', 'PyYAML==5.2', 'wheel==0.33.6', 'idna==2.10', 'MarkupSafe==1.1.1', 'pbr==5.8.1', 'netaddr==0.7.19', 'pyaml==21.10.1', 'urllib3==1.25.11', 'charmhelpers==0.20.24', 'tenacity==5.0.3', 'charms.reactive==1.5.0', 'six==1.16.0', 'certifi==2021.10.8', 'Tempita==0.5.2']' returned non-zero exit status 1.
unit-prometheus2-0: 11:14:59 ERROR juju.worker.uniter.operation hook "install" (via explicit, bespoke hook script) failed: exit status 1
unit-prometheus2-0: 11:14:59 INFO juju.worker.uniter awaiting error resolution for "install" hook