Wheel fails without useful error message when --wheel-dir not writable

[timb07]

When wheel is invoked specifying a non-writable destination directory with --wheel-dir, it fails but doesn't give an error indicating the cause of the failure.

$ pip3 wheel --wheel-dir=not_writable_directory .
Processing /home/user/example_pkg
Building wheels for collected packages: example-pkg
  Running setup.py bdist_wheel for example-pkg ... done
  Running setup.py clean for example-pkg
Failed to build example-pkg
ERROR: Failed to build one or more wheels

Adding -vvv to the pip3 command line provides more output but still no useful error message.

I would expect to see something like:

Failed to write not_writable_directory/example_pkg-0.0.1-py3-none-any.whl: permission denied

Reproducable using the minimal example at https://packaging.python.org/tutorials/packaging-projects/.

[agronholm]

Why are you reporting a problem with pip here? python setup.py bdist_wheel does fail with a proper error message if the wheel directory isn't writable (such as error: [Errno 13] Permission denied: 'dist/wheel-1.0.0b1-py2.py3-none-any.whl').