def get_package_info(srcdir='.', exclude=()):
    """
    Collates all of the information for building all subpackages
    and returns a dictionary of keyword arguments that can
    be passed directly to `distutils.setup`.

    The purpose of this function is to allow subpackages to update the
    arguments to the package's ``setup()`` function in its setup.py
    script, rather than having to specify all extensions/package data
    directly in the ``setup.py``.  See Astropy's own
    ``setup.py`` for example usage and the Astropy development docs
    for more details.

    This function obtains that information by iterating through all
    packages in ``srcdir`` and locating a ``setup_package.py`` module.
    This module can contain the following functions:
    ``get_extensions()``, ``get_package_data()``,
    ``get_build_options()``, and ``get_external_libraries()``.

    Each of those functions take no arguments.

    - ``get_extensions`` returns a list of
      `distutils.extension.Extension` objects.

    - ``get_package_data()`` returns a dict formatted as required by
      the ``package_data`` argument to ``setup()``.

    - ``get_build_options()`` returns a list of tuples describing the
      extra build options to add.

    - ``get_external_libraries()`` returns
      a list of libraries that can optionally be built using external
      dependencies.
    """
    ext_modules = []
    packages = []
    package_dir = {}

    # Read in existing package data, and add to it below
    setup_cfg = os.path.join(srcdir, 'setup.cfg')
    if os.path.exists(setup_cfg):
        conf = read_configuration(setup_cfg)
        if 'options' in conf and 'package_data' in conf['options']:
            package_data = conf['options']['package_data']
        else:
            package_data = {}
    else:
        package_data = {}

    if exclude:
        warnings.warn(
            "Use of the exclude parameter is no longer supported since it does "
            "not work as expected. Use add_exclude_packages instead. Note that "
            "it must be called prior to any other calls from setup helpers.",
            AstropyDeprecationWarning)

    # Use the find_packages tool to locate all packages and modules
    packages = find_packages(srcdir, exclude=exclude)

    # Update package_dir if the package lies in a subdirectory
    if srcdir != '.':
        package_dir[''] = srcdir

    # For each of the setup_package.py modules, extract any
    # information that is needed to install them.  The build options
    # are extracted first, so that their values will be available in
    # subsequent calls to `get_extensions`, etc.
    for setuppkg in iter_setup_packages(srcdir, packages):
        if hasattr(setuppkg, 'get_build_options'):
            options = setuppkg.get_build_options()
            for option in options:
                add_command_option('build', *option)
        if hasattr(setuppkg, 'get_external_libraries'):
            libraries = setuppkg.get_external_libraries()
            for library in libraries:
                add_external_library(library)

    for setuppkg in iter_setup_packages(srcdir, packages):
        # get_extensions must include any Cython extensions by their .pyx
        # filename.
        if hasattr(setuppkg, 'get_extensions'):
            ext_modules.extend(setuppkg.get_extensions())
        if hasattr(setuppkg, 'get_package_data'):
            package_data.update(setuppkg.get_package_data())

    # Locate any .pyx files not already specified, and add their extensions in.
    # The default include dirs include numpy to facilitate numerical work.
    ext_modules.extend(get_cython_extensions(srcdir, packages, ext_modules,
                                             ['numpy']))

    # Now remove extensions that have the special name 'skip_cython', as they
    # exist Only to indicate that the cython extensions shouldn't be built
    for i, ext in reversed(list(enumerate(ext_modules))):
        if ext.name == 'skip_cython':
            del ext_modules[i]

    # On Microsoft compilers, we need to pass the '/MANIFEST'
    # commandline argument.  This was the default on MSVC 9.0, but is
    # now required on MSVC 10.0, but it doesn't seem to hurt to add
    # it unconditionally.
    if get_compiler_option() == 'msvc':
        for ext in ext_modules:
            ext.extra_link_args.append('/MANIFEST')

    return {
        'ext_modules': ext_modules,
        'packages': packages,
        'package_dir': package_dir,
        'package_data': package_data,
        }
Collates all of the information for building all subpackages
    and returns a dictionary of keyword arguments that can
    be passed directly to `distutils.setup`.

    The purpose of this function is to allow subpackages to update the
    arguments to the package's ``setup()`` function in its setup.py
    script, rather than having to specify all extensions/package data
    directly in the ``setup.py``.  See Astropy's own
    ``setup.py`` for example usage and the Astropy development docs
    for more details.

    This function obtains that information by iterating through all
    packages in ``srcdir`` and locating a ``setup_package.py`` module.
    This module can contain the following functions:
    ``get_extensions()``, ``get_package_data()``,
    ``get_build_options()``, and ``get_external_libraries()``.

    Each of those functions take no arguments.

    - ``get_extensions`` returns a list of
      `distutils.extension.Extension` objects.

    - ``get_package_data()`` returns a dict formatted as required by
      the ``package_data`` argument to ``setup()``.

    - ``get_build_options()`` returns a list of tuples describing the
      extra build options to add.

    - ``get_external_libraries()`` returns
      a list of libraries that can optionally be built using external
      dependencies.