aiidalab CLI raises when an invalid commit/branch is specified

[danielhollas]

I just hit this when I was trying to install my app via CLI directly from Github and made a typo in a branch name.

Traceback (most recent call last):
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/git_util.py", line 177, in read_bytes
    return run(
  File "/opt/conda/lib/python3.9/subprocess.py", line 528, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['git', 'show', 'deps/install-xtb-openmpi:.']' returned non-zero exit status 128.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/conda/bin/aiidalab", line 10, in <module>
    sys.exit(cli())
  File "/opt/conda/lib/python3.9/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/opt/conda/lib/python3.9/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/opt/conda/lib/python3.9/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/opt/conda/lib/python3.9/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/opt/conda/lib/python3.9/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/__main__.py", line 401, in install
    install_candidates = {
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/__main__.py", line 402, in <dictcomp>
    requirement: _find_version_to_install(
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/__main__.py", line 280, in _find_version_to_install
    with fetch_from_url(app_requirement.url) as repo:
  File "/opt/conda/lib/python3.9/contextlib.py", line 119, in __enter__
    return next(self.gen)
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/fetch.py", line 114, in fetch_from_url
    with _fetch_from_git_https(urlunsplit(ps._replace(scheme="https"))) as path:
  File "/opt/conda/lib/python3.9/contextlib.py", line 119, in __enter__
    return next(self.gen)
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/fetch.py", line 75, in _fetch_from_git_https
    with _fetch_from_path(git_path) as path:
  File "/opt/conda/lib/python3.9/contextlib.py", line 119, in __enter__
    return next(self.gen)
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/fetch.py", line 30, in _fetch_from_path
    with tarfile.open(fileobj=BytesIO(path.read_bytes())) as tar_file:
  File "/opt/conda/lib/python3.9/site-packages/aiidalab/git_util.py", line 194, in read_bytes
    raise ValueError(f"Unknown commit: {self.commit}")
ValueError: Unknown commit: deps/install-xtb-openmpi