[feature request] SupervisorTransport can't handle reconnects in Python >=2.7

[sfriesel]

Since Python 2.7, xmlrpclib.Transport has a close method and a connection retry (https://github.com/python/cpython/blob/2.7/Lib/xmlrpclib.py#L1277) when a persistent connection gets closed. The way SupervisorTransport overrides the class breaks this feature. This could be fixed by reducing the amount of overrides in SupervisorTransport to get the base class behavior or by implementing the close method.

Related to #650

[sfriesel]

N.B.: this is not available in 2.6

[mnaberez]

The overrides in SupervisorTransport came about because of either adding support for persistent connections, or adding support for Unix domain sockets. The SupervisorTransport code was originally developed for Python 2.3 and hasn't changed much since then. I recall changes to the base xmlrpclib.Transport in later Python versions, but I don't remember the details.

On Supervisor 3.x, we support Python 2.4+ but not Python 3. On Supervisor 4.x (master branch), we will support Python 2.6+ and Python 3.2+.

Since the master branch has dropped support for Python 2.4 and 2.5, it may be possible to remove some of the overrides in SupervisorTransport without changing our existing functionality. If that's true, I'd be happy to merge a pull request, but we will keep Python 2.6 support for the foreseeable future.

[mnaberez]

N.B.: this is not available in 2.6

Update: In Supervisor 4.0.0 (released April 2019), we dropped support for Python 2.6. Supervisor now requires Python 2.7 or 3.4+.