Fix unclosed socket in TraCI Connection initializer

[Gamenot]

Solution

I propose a minor fix to eliminate a resource warning originating from the traci.Connection initializer.

The second client example in the socket Python library documentation indicates that socket.connect() may not clean itself up if it generates an exception: https://docs.python.org/3.5/library/socket.html#example

# Echo client program
...
    try:
        s.connect(sa)
    except OSError as msg:
        s.close()
        s = None
        continue
    break
...

Impact

Using traci.connect() would cause an unclosed socket to get garbage collected and give a resource warning. The error is known about and caught at the traci.connect() level without clean-up of the socket.

https://github.com/eclipse/sumo/blob/49ba1525d34ae23b515d08cf2643975a1f7b169c/tools/traci/main.py#L89-L111

It was causing warnings to show up and mess with logging, requiring a workaround. A stranger quickly reached out to make it known that the issue was not unique to us: huawei-noah/SMARTS#1373

[Gamenot]

I have kept the socket.error alias of OSError for consistency's sake.

[behrisch]

Thanks!