Retrieve a file from the RCSB.

def retrieve_file_from_RCSB(http_connection, resource, silent = True):
    '''Retrieve a file from the RCSB.'''
    if not silent:
        colortext.printf("Retrieving %s from RCSB" % os.path.split(resource)[1], color = "aqua")
    return http_connection.get(resource)