Does not deploy on Xenial due to MarkupSafe dependency relying on Python 3.6

[Paul Goins]

I tried to deploy easyrsa on a Xenial LXD recently for test purposes, and found that it no longer deploys cleanly on Xenial. It does deploy fine on Bionic and Focal.

On Xenial, I can see this in the Juju unit log, assuming the unit log level is set to debug:

2021-07-22 20:47:09 DEBUG install Collecting MarkupSafe
2021-07-22 20:47:10 DEBUG install Complete output from command python setup.py egg_info:
2021-07-22 20:47:10 DEBUG install Traceback (most recent call last):
2021-07-22 20:47:10 DEBUG install File "<string>", line 1, in <module>
2021-07-22 20:47:10 DEBUG install File "/tmp/pip-install-000tad_z/MarkupSafe/setup.py", line 61, in <module>
2021-07-22 20:47:10 DEBUG install run_setup(True)
2021-07-22 20:47:10 DEBUG install File "/tmp/pip-install-000tad_z/MarkupSafe/setup.py", line 44, in run_setup
2021-07-22 20:47:10 DEBUG install ext_modules=ext_modules if with_binary else [],
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/__init__.py", line 145, in setup
2021-07-22 20:47:10 DEBUG install return distutils.core.setup(**attrs)
2021-07-22 20:47:10 DEBUG install File "/usr/lib/python3.5/distutils/core.py", line 121, in setup
2021-07-22 20:47:10 DEBUG install dist.parse_config_files()
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/dist.py", line 701, in parse_config_files
2021-07-22 20:47:10 DEBUG install ignore_option_errors=ignore_option_errors)
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/config.py", line 121, in parse_configuration
2021-07-22 20:47:10 DEBUG install meta.parse()
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/config.py", line 426, in parse
2021-07-22 20:47:10 DEBUG install section_parser_method(section_options)
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/config.py", line 399, in parse_section
2021-07-22 20:47:10 DEBUG install self[name] = value
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/config.py", line 184, in __setitem__
2021-07-22 20:47:10 DEBUG install value = parser(value)
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/config.py", line 514, in _parse_version
2021-07-22 20:47:10 DEBUG install version = self._parse_attr(value, self.package_dir)
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/site-packages/setuptools/config.py", line 349, in _parse_attr
2021-07-22 20:47:10 DEBUG install module = import_module(module_name)
2021-07-22 20:47:10 DEBUG install File "/var/lib/juju/agents/unit-easyrsa-0/.venv/lib/python3.5/importlib/__init__.py", line 126, in import_module
2021-07-22 20:47:10 DEBUG install return _bootstrap._gcd_import(name[level:], package, level)
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap>", line 986, in _gcd_import
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap>", line 969, in _find_and_load
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap_external>", line 661, in exec_module
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap_external>", line 767, in get_code
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap_external>", line 727, in source_to_code
2021-07-22 20:47:10 DEBUG install File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
2021-07-22 20:47:10 DEBUG install File "/tmp/pip-install-000tad_z/MarkupSafe/src/markupsafe/__init__.py", line 112
2021-07-22 20:47:10 DEBUG install return f"{self.__class__.__name__}({super().__repr__()})"
2021-07-22 20:47:10 DEBUG install ^
2021-07-22 20:47:10 DEBUG install SyntaxError: invalid syntax
2021-07-22 20:47:10 DEBUG install
2021-07-22 20:47:10 DEBUG install ----------------------------------------
2021-07-22 20:47:10 WARNING install Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-000tad_z/MarkupSafe/
2021-07-22 20:47:10 WARNING install Traceback (most recent call last):
2021-07-22 20:47:10 WARNING install File "/var/lib/juju/agents/unit-easyrsa-0/charm/hooks/install", line 8, in <module>
2021-07-22 20:47:10 WARNING install basic.bootstrap_charm_deps()
2021-07-22 20:47:10 WARNING install File "lib/charms/layer/basic.py", line 208, in bootstrap_charm_deps
2021-07-22 20:47:10 WARNING install env=_get_subprocess_env())
2021-07-22 20:47:10 WARNING install File "/usr/lib/python3.5/subprocess.py", line 581, in check_call
2021-07-22 20:47:10 WARNING install raise CalledProcessError(retcode, cmd)
2021-07-22 20:47:10 WARNING install subprocess.CalledProcessError: Command '['/var/lib/juju/agents/unit-easyrsa-0/.venv/bin/pip', 'install', '-U', '--force-reinstall', '--no-index', '--no-cache-dir', '-f', 'wheelhouse', 'PyYAML', 'pbr', 'wheel', 'Jinja2', 'charmhelpers', 'six', 'netaddr', 'charms.reactive', 'pyaml', 'Tempita', 'MarkupSafe']' returned non-zero exit status 1
2021-07-22 20:47:10 ERROR juju.worker.uniter.operation runhook.go:139 hook "install" (via explicit, bespoke hook script) failed: exit status 1

The error occurs due to a Python 3.6 f-string, which won't work on Xenial's Python 3.5.

It may be necessary to pin MarkupSafe to an older version to preserve Xenial support for this charm.

[Paul Goins (vultaire)]

Alternatively, xenial could be removed as a supported release for easyrsa.

[Paul Goins (vultaire)]

It appears this was taken care of by Adam Dyess in July of this year, changeset 2f4ade054b861c41acc39ae7e24bd581f0c1cb13. Marking as done.

[Paul Goins (vultaire)]

Released; earliest version is github tag 1.24+ck1, branch release_1.24. Also confirmed present in the trunk.