InvalidRequirement when installing apache airflow with gcp_api extra

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

Poetry
Version: 1.0.0a2
Python:  3.6.6

Virtualenv
Python:         3.6.6
Implementation: CPython
Path:           /Users/benjamin/.pyenv/versions/3.6.6/envs/poetry
Valid:          True

System
Platform: darwin
OS:       posix
Python:   /Users/benjamin/.pyenv/versions/3.6.6

Issue

# On a clean virtualenv
$ poetry add apache-airflow --extras gcp_api -v

Using virtualenv: /Users/benjamin/.pyenv/versions/3.6.6/envs/poetry
Using version ^1.10 for apache-airflow

Updating dependencies
Resolving dependencies... (1.3s)

[InvalidRequirement]
Invalid requirement, parse error at "'; <empty'"

Traceback (most recent call last):
  File "/Users/benjamin/.poetry/lib/poetry/_vendor/py3.6/clikit/console_application.py", line 131, in run
    status_code = command.handle(parsed_args, io)
  File "/Users/benjamin/.poetry/lib/poetry/_vendor/py3.6/clikit/api/command/command.py", line 112, in handle
    status_code = self._do_handle(args, io)
  File "/Users/benjamin/.poetry/lib/poetry/_vendor/py3.6/clikit/api/command/command.py", line 160, in _do_handle
    return getattr(handler, handler_method)(args, io, self)
  File "/Users/benjamin/.poetry/lib/poetry/_vendor/py3.6/cleo/commands/command.py", line 92, in wrap_handle
    return self.handle()
  File "/Users/benjamin/.poetry/lib/poetry/console/commands/add.py", line 135, in handle
    status = installer.run()
  File "/Users/benjamin/.poetry/lib/poetry/installation/installer.py", line 74, in run
    self._do_install(local_repo)
  File "/Users/benjamin/.poetry/lib/poetry/installation/installer.py", line 214, in _do_install
    ops = solver.solve(use_latest=whitelist)
  File "/Users/benjamin/.poetry/lib/poetry/puzzle/solver.py", line 38, in solve
    packages, depths = self._solve(use_latest=use_latest)
  File "/Users/benjamin/.poetry/lib/poetry/puzzle/solver.py", line 171, in _solve
    self._package, self._provider, locked=locked, use_latest=use_latest
  File "/Users/benjamin/.poetry/lib/poetry/mixology/__init__.py", line 7, in resolve_version
    return solver.solve()
  File "/Users/benjamin/.poetry/lib/poetry/mixology/version_solver.py", line 79, in solve
    next = self._choose_package_version()
  File "/Users/benjamin/.poetry/lib/poetry/mixology/version_solver.py", line 380, in _choose_package_version
    for incompatibility in self._provider.incompatibilities_for(version):
  File "/Users/benjamin/.poetry/lib/poetry/puzzle/provider.py", line 435, in incompatibilities_for
    for dep in dependencies
  File "/Users/benjamin/.poetry/lib/poetry/puzzle/provider.py", line 435, in <listcomp>
    for dep in dependencies
  File "/Users/benjamin/.poetry/lib/poetry/packages/package.py", line 346, in to_dependency
    return dependency_from_pep_508(name)
  File "/Users/benjamin/.poetry/lib/poetry/packages/__init__.py", line 34, in dependency_from_pep_508
    req = Requirement(name)
  File "/Users/benjamin/.poetry/lib/poetry/version/requirements.py", line 202, in __init__
    requirement_string[e.loc : e.loc + 8]

[djetelina]

Still an issue, both under 0.12.17 and 1.0.0a4

[Paikan]

@sdispater would you mind reopening this issue as it does not seem to be fixed?