Installing googleanalytics plugin returns "BackendUnavailable" error

From everything I can tell, it looks like this error typically revolves around compatibility issues with python2 and python3. I'm running ckan 2.8, which should be compatible.

```
pip install -e git+https://github.com/ckan/ckanext-googleanalytics.git#egg=ckanext-googleanalytics
DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Obtaining ckanext-googleanalytics from git+https://github.com/ckan/ckanext-googleanalytics.git#egg=ckanext-googleanalytics
Updating /usr/lib/ckan/venv/src/ckanext-googleanalytics clone
Running command git fetch -q --tags
Running command git reset --hard -q cbee3f06d6374492e12c204af7ef1ddd3ed00a4a
Installing build dependencies ... done
Getting requirements to build wheel ... done
ERROR: Exception:
Traceback (most recent call last):
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/cli/base_command.py", line 188, in _main
status = self.run(options, args)
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/cli/req_command.py", line 185, in wrapper
return func(self, options, args)
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/commands/install.py", line 333, in run
reqs, check_supported_wheels=not options.target_dir
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/resolution/legacy/resolver.py", line 179, in resolve
discovered_reqs.extend(self._resolve_one(requirement_set, req))
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/resolution/legacy/resolver.py", line 362, in _resolve_one
abstract_dist = self._get_abstract_dist_for(req_to_install)
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/resolution/legacy/resolver.py", line 300, in _get_abstract_dist_for
return self.preparer.prepare_editable_requirement(req)
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/operations/prepare.py", line 532, in prepare_editable_requirement
req, self.req_tracker, self.finder, self.build_isolation,
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/operations/prepare.py", line 91, in _get_prepared_distribution
abstract_dist.prepare_distribution_metadata(finder, build_isolation)
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/distributions/sdist.py", line 38, in prepare_distribution_metadata
self._setup_isolation(finder)
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_internal/distributions/sdist.py", line 96, in _setup_isolation
reqs = backend.get_requires_for_build_wheel()
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/wrappers.py", line 161, in get_requires_for_build_wheel
'config_settings': config_settings
File "/usr/lib/ckan/venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/wrappers.py", line 265, in _call_hook
raise BackendUnavailable(data.get('traceback', ''))
BackendUnavailable
```

Start by reproducing the shown pip install command in the reported CKAN 2.8 and Python 2.7 environment. Inspect the PEP 517 build-isolation traceback around pip's BackendUnavailable error and determine whether the plugin or its build dependencies cause it. Done means the installation path is identified and the plugin installs successfully or its supported environment is documented.

Written by the indexing model from the issue text.