Provide nice UX when a user needs to configure git user.name and user.email

[alexlatchford]

vaishnavig@ZG02169 Code % battenberg -O new_dir install [email protected]:devex/archetypes/python-lib-archetype.git
Traceback (most recent call last):
  File “/usr/local/bin/battenberg”, line 8, in <module>
    sys.exit(main())
  File “/usr/local/lib/python3.9/site-packages/click/core.py”, line 829, in _call_
    return self.main(*args, **kwargs)
  File “/usr/local/lib/python3.9/site-packages/click/core.py”, line 782, in main
    rv = self.invoke(ctx)
  File “/usr/local/lib/python3.9/site-packages/click/core.py”, line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File “/usr/local/lib/python3.9/site-packages/click/core.py”, line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File “/usr/local/lib/python3.9/site-packages/click/core.py”, line 610, in invoke
    return callback(*args, **kwargs)
  File “/usr/local/lib/python3.9/site-packages/click/decorators.py”, line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File “/usr/local/lib/python3.9/site-packages/battenberg/cli.py”, line 80, in install
    battenberg = Battenberg(open_or_init_repository(ctx.obj[‘target’], template, initial_branch))
  File “/usr/local/lib/python3.9/site-packages/battenberg/utils.py”, line 44, in open_or_init_repository
    repo.default_signature,
KeyError: “config value ‘user.name’ was not found”

This massive stacktrace is a pretty terrible experience for an easy self-service fix for users, they just need to set git config user.name <my name> and git config user.email <my email> as pygit2 needs that to infer the default_signature.