def sync(cb):
while <NUM_LIT:1>:<EOL><INDENT>try:<EOL><INDENT>cb()<EOL><DEDENT>except SshNonblockingTryAgainException:<EOL><INDENT>pass<EOL><DEDENT>else:<EOL><INDENT>break<EOL><DEDENT><DEDENT>
A function that will repeatedly invoke a callback until it doesn't 
    return a try-again error.