def available_sources(sources):
for dirs, name in sources:<EOL><INDENT>for directory in dirs:<EOL><INDENT>fn = os.path.join(directory, name) + '<STR_LIT>'<EOL>if os.path.isfile(fn):<EOL><INDENT>yield fn<EOL><DEDENT><DEDENT><DEDENT>
Yield the sources that are present.