def run(command, shell=True, pty=True):
    """
    Helper function.
    Runs a command with SSH agent forwarding enabled.
    Note:: Fabric (and paramiko) can't forward your SSH agent. 
    This helper uses your system's ssh to do so.
    """
real_command = command
if shell:
    cwd = env.get('cwd', '')
if cwd:
    cwd = 'cd %s && ' % _shell_escape(cwd)
Run ssh-add with Fabric in a machine