def githubtunnel(user1, server1, user2, server2, port, verbose, stanford=False):
if stanford:<EOL><INDENT>port_shift = <NUM_LIT:1><EOL><DEDENT>else:<EOL><INDENT>port_shift = <NUM_LIT:0><EOL><DEDENT>command1 = '<STR_LIT>'.format(port-<NUM_LIT:1>-port_shift, server2, user1, server1)<EOL>command2 = '<STR_LIT>'.format(port-port_shift, port-port_shift-<NUM_LIT:1>, user2)<EOL>command3 = '<STR_LIT>'.format(port, port-<NUM_LIT:1>, user2)<EOL>if verbose:<EOL><INDENT>print(command1)<EOL>if stanford:<EOL><INDENT>print(command2)<EOL><DEDENT>print(command3)<EOL><DEDENT>try:<EOL><INDENT>call(shlex.split(command1))<EOL>if stanford:<EOL><INDENT>call(shlex.split(command2))<EOL><DEDENT>call(shlex.split(command3))<EOL><DEDENT>except:<EOL><INDENT>print('<STR_LIT>')<EOL>pass<EOL><DEDENT>
Opens a nested tunnel, first to *user1*@*server1*, then to *user2*@*server2*, for accessing on *port*.

If *verbose* is true, prints various ssh commands.

If *stanford* is true, shifts ports up by 1.

Attempts to get *user1*, *user2* from environment variable ``USER_NAME`` if called from the command line.