pip: pip 10 is unable to install from non-editable VCS URLs

• Pip version: 10.0.0
• Python version: 3.5.4
• Operating system: Linux

Description:

I’m trying to install a package from Git.

What I’ve run:

$ pip3 install git+ssh://git@example.com/mypackage.git#egg=mypackage

Building wheels for collected packages: mypackage
Exception:
Traceback (most recent call last):
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/basecommand.py", line 228, in main
    status = self.run(options, args)
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/commands/install.py", line 305, in run
    session=session, autobuilding=True
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/wheel.py", line 773, in build
    python_tag=python_tag,
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/wheel.py", line 633, in _build_one
    python_tag=python_tag)
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/wheel.py", line 637, in _build_one_inside_env
    if self.__build_one(req, temp_dir.path, python_tag=python_tag):
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/wheel.py", line 663, in __build_one
    base_args = self._base_setup_args(req)
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/wheel.py", line 659, in _base_setup_args
    SETUPTOOLS_SHIM % req.setup_py
  File "/home/p/local/lib/python3.5/site-packages/pip/_internal/req/req_install.py", line 416, in setup_py
    assert self.source_dir, "No source dir for %s" % self
AssertionError: No source dir for mypackage from git+ssh://git@example.com/mypackage.git#egg=mypackage in /home/p/local/lib/python3.5/site-packages

If I uninstall the package and then install, it works. But it continues to fail when trying install again.