Load a module named ``module`` from given search``path``

    The module path prefix is set according to the ``prefix`` argument.
    By defualt the module is loaded as if it comes from a global
    'db_migrations' package.  As such, it may conflict with any 'db_migration'
    package. The module can be looked up in ``sys.modules`` as
    ``db_migration.MODNAME`` where ``MODNAME`` is the name supplied as
    ``module`` argument. Keep in mind that relative imports from within the
    module depend on this prefix.

    This function raises an ``ImportError`` exception if module is not found.

    :param module:  name of the module to load
    :param package: package object
    :returns:       module object

def load_mod(module, package):
    """ Load a module named ``module`` from given search``path``

    The module path prefix is set according to the ``prefix`` argument.
    By defualt the module is loaded as if it comes from a global
    'db_migrations' package.  As such, it may conflict with any 'db_migration'
    package. The module can be looked up in ``sys.modules`` as
    ``db_migration.MODNAME`` where ``MODNAME`` is the name supplied as
    ``module`` argument. Keep in mind that relative imports from within the
    module depend on this prefix.

    This function raises an ``ImportError`` exception if module is not found.

    :param module:  name of the module to load
    :param package: package object
    :returns:       module object
    """
    name = '%s.%s' % (package.__name__, module)
    if name in sys.modules:
        return sys.modules[name]
    return importlib.import_module(name, package=package.__name__)