def fix_column_name(val):
    """
    Fixes column names so that they are compatible with Numpy on
    Python 2.  Raises a ValueError exception if the column name
    contains Unicode characters, which can not reasonably be used as a
    column name.
    """
    if val is not None:
        try:
            val = str(val)
        except UnicodeEncodeError:
            raise
    return val
