Unfriendly error message when unicode is passed to package_dir or packages

Originally reported by: jaraco (Bitbucket: jaraco, GitHub: jaraco)

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Adding __future__.unicode_literals causes setup.py scripts to fail. In the mailman project, here is an example error when running python2 setup.py build:

running build
running build_py
Traceback (most recent call last):
  File "setup.py", line 112, in <module>
    test_suite = 'nose2.collector.collector',
  File "C:\Program Files\Python27\lib\distutils\core.py", line 152, in setup
    dist.run_commands()
  File "C:\Program Files\Python27\lib\distutils\dist.py", line 953, in run_commands
    self.run_command(cmd)
  File "C:\Program Files\Python27\lib\distutils\dist.py", line 972, in run_command
    cmd_obj.run()
  File "C:\Program Files\Python27\lib\distutils\command\build.py", line 127, in run
    self.run_command(cmd_name)
  File "C:\Program Files\Python27\lib\distutils\cmd.py", line 326, in run_command
    self.distribution.run_command(command)
  File "C:\Program Files\Python27\lib\distutils\dist.py", line 972, in run_command
    cmd_obj.run()
  File "build\bdist.win-amd64\egg\setuptools\command\build_py.py", line 42, in run
  File "C:\Program Files\Python27\lib\distutils\command\build_py.py", line 372, in build_packages
    self.build_module(module, module_file, package)
  File "build\bdist.win-amd64\egg\setuptools\command\build_py.py", line 60, in build_module
  File "C:\Program Files\Python27\lib\distutils\command\build_py.py", line 333, in build_module
    "'package' must be a string (dot-separated), list, or tuple")
TypeError: 'package' must be a string (dot-separated), list, or tuple

A different error occurs when using 'develop':

running develop
error: 'egg_base' must be a directory name (got `src`)

Setuptools could make this error message nicer.

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• Bitbucket: https://bitbucket.org/pypa/setuptools/issue/190