List command raises errors on master branch

[jambonrose]

After installing the master branch of pipsi today, I am unable to use the list command.

$ curl https://raw.githubusercontent.com/mitsuhiko/pipsi/master/get-pipsi.py | python3.7 - --src 'git+https://github.com/mitsuhiko/pipsi.git#egg=pipsi'
$ # add export PATH=/Users/andrew/.local/bin:$PATH to .profile
$ pipsi --version
pipsi, version 0.10.dev0, python /Users/andrew/.local/venvs/pipsi/bin/python3.7
$ pipsi list
Traceback (most recent call last):
  File "/Users/andrew/.local/bin/pipsi", line 11, in <module>
    load_entry_point('pipsi==0.10.dev0', 'console_scripts', 'pipsi')()
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/decorators.py", line 27, in new_func
    return f(get_current_context().obj, *args, **kwargs)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/pipsi/__init__.py", line 538, in list_cmd
    for venv, scripts in repo.list_everything()
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/pipsi/__init__.py", line 434, in list_everything
    info = self.get_package_info(venv_path)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/pipsi/__init__.py", line 304, in get_package_info
    with open(package_info_file_path, 'r') as fh:
FileNotFoundError: [Errno 2] No such file or directory: '/Users/andrew/.local/venvs/pipsi/package_info.json'
$ pipsi install poetry  # output removed, no problems!
$ pipsi list
Traceback (most recent call last):
  File "/Users/andrew/.local/bin/pipsi", line 11, in <module>
    load_entry_point('pipsi==0.10.dev0', 'console_scripts', 'pipsi')()
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/click/decorators.py", line 27, in new_func
    return f(get_current_context().obj, *args, **kwargs)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/pipsi/__init__.py", line 538, in list_cmd
    for venv, scripts in repo.list_everything()
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/pipsi/__init__.py", line 434, in list_everything
    info = self.get_package_info(venv_path)
  File "/Users/andrew/.local/venvs/pipsi/lib/python3.7/site-packages/pipsi/__init__.py", line 304, in get_package_info
    with open(package_info_file_path, 'r') as fh:
FileNotFoundError: [Errno 2] No such file or directory: '/Users/andrew/.local/venvs/pipsi/package_info.json'

I originally posted the error above in #169, but given that the error is about a different path and that it is still appearing even after installation, I believe this may actually be a separate issue.