def changed(self, src, path, dest):
try:<EOL><INDENT>mtime = os.path.getmtime(os.path.join(src, path))<EOL>self._build(src, path, dest, mtime)<EOL><DEDENT>except EnvironmentError as e:<EOL><INDENT>logging.error("<STR_LIT>".format(<EOL>termcolor.colored(path, "<STR_LIT>", attrs=["<STR_LIT>"]),<EOL>e.args[<NUM_LIT:0>]<EOL>))<EOL><DEDENT>
Called whenever `path` is changed in the source folder `src`. `dest`
        is the output folder. The default implementation calls `build` after
        determining that the input file is newer than any of the outputs, or
        any of the outputs does not exist.