[BUG] --offline mode failing due to issues with file location

[iameskild]

Due to a potential upstream change, the conda-vendor --offline mode failed to build because of issues handling paths related to repodata.json. Adding a test to ensure --offline mode is working as expected might catch some of these changes.

Traceback (most recent call last):
  File "/opt/conda/lib/python3.9/site-packages/conda/exceptions.py", line 1082, in __call__
    return func(*args, **kwargs)
  File "/opt/conda/lib/python3.9/site-packages/conda_env/cli/main.py", line 80, in do_call
    exit_code = getattr(module, func_name)(args, parser)
  File "/opt/conda/lib/python3.9/site-packages/conda_env/cli/main_create.py", line 142, in execute
    result[installer_type] = installer.install(prefix, pkg_specs, args, env)
  File "/opt/conda/lib/python3.9/site-packages/conda_env/installers/conda.py", line 50, in install
    unlink_link_transaction = solver.solve_for_transaction(
  File "/opt/conda/lib/python3.9/site-packages/conda/core/solve.py", line 152, in solve_for_transaction
    unlink_precs, link_precs = self.solve_for_diff(update_modifier, deps_modifier,
  File "/opt/conda/lib/python3.9/site-packages/conda/core/solve.py", line 195, in solve_for_diff
    final_precs = self.solve_final_state(update_modifier, deps_modifier, prune, ignore_pinned,
  File "/opt/conda/lib/python3.9/site-packages/conda/core/solve.py", line 300, in solve_final_state
    ssc = self._collect_all_metadata(ssc)
  File "/opt/conda/lib/python3.9/site-packages/conda/common/io.py", line 88, in decorated
    return f(*args, **kwds)
  File "/opt/conda/lib/python3.9/site-packages/conda/core/solve.py", line 463, in _collect_all_metadata
    index, r = self._prepare(prepared_specs)
  File "/opt/conda/lib/python3.9/site-packages/conda/core/solve.py", line 1058, in _prepare
    reduced_index = get_reduced_index(self.prefix, self.channels,
  File "/opt/conda/lib/python3.9/site-packages/conda/core/index.py", line 288, in get_reduced_index
    new_records = SubdirData.query_all(spec, channels=channels, subdirs=subdirs,
  File "/opt/conda/lib/python3.9/site-packages/conda/core/subdir_data.py", line 140, in query_all
    result = tuple(concat(executor.map(subdir_query, channel_urls)))
  File "/opt/conda/lib/python3.9/concurrent/futures/_base.py", line 609, in result_iterator
    yield fs.pop().result()
  File "/opt/conda/lib/python3.9/concurrent/futures/_base.py", line 446, in result
    return self.__get_result()
  File "/opt/conda/lib/python3.9/concurrent/futures/_base.py", line 391, in __get_result
    raise self._exception
  File "/opt/conda/lib/python3.9/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/opt/conda/lib/python3.9/site-packages/conda/core/subdir_data.py", line 132, in <lambda>
    subdir_query = lambda url: tuple(SubdirData(Channel(url), repodata_fn=repodata_fn).query(
  File "/opt/conda/lib/python3.9/site-packages/conda/core/subdir_data.py", line 145, in query
    self.load()
  File "/opt/conda/lib/python3.9/site-packages/conda/core/subdir_data.py", line 210, in load
    _internal_state = self._load()
  File "/opt/conda/lib/python3.9/site-packages/conda/core/subdir_data.py", line 407, in _load
    _internal_state = self._process_raw_repodata_str(raw_repodata_str)
  File "/opt/conda/lib/python3.9/site-packages/conda/core/subdir_data.py", line 485, in _process_raw_repodata_str
    assert subdir == self.channel.subdir
AssertionError