get_python_dll() sometimes doesn't fail when when python_dll does not exist

[subthedubdub]

In setup.py, the function get_python_dll() contains the following lines at the end:

   ldlibrary = sysconfig.get_config_var('LDLIBRARY')
    libdir = sysconfig.get_config_var('LIBDIR')
    if ldlibrary and libdir:
        return os.path.join(libdir, ldlibrary)
    raise RuntimeError('no python dll')

Weirdly, it is possible that os.path.join(libdir, ldlibrary) does not exist in certain setups (as I observed at work, where the value returned was /var/tmp/*).

I recommended running os.path.exists prior to returning.

[sashkab]

This issue will be addressed by PyQ 4.2.0, fixed internally.

Internal issue 1024.