Make RospyLogger.findCaller compatible with Python3 (also, unbreak ROS on Python3)

[kartikmohta]

Due to the change in #1043, ROS was broken on Python3. The findCaller function in Python3 logging module takes 2 arguments (including self) compared to only 1 (self) in Python2 and returns 4 values instead of 3 in Python2.

Without this patch, roscore doesn't even start:

$ roscore
... logging to /home/kartikmohta/.ros/log/30a1f112-78a5-11e7-bdaf-507b9d9f0576/roslaunch-nyx-23629.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

Traceback (most recent call last):
  File "/opt/ros/lunar_py3/lib/python3.6/site-packages/roslaunch/__init__.py", line 306, in main
    p.start()
  File "/opt/ros/lunar_py3/lib/python3.6/site-packages/roslaunch/parent.py", line 264, in start
    self.logger.info("starting roslaunch parent run")
  File "/usr/lib/python3.6/logging/__init__.py", line 1306, in info
    self._log(INFO, msg, args, **kwargs)
  File "/usr/lib/python3.6/logging/__init__.py", line 1430, in _log
    fn, lno, func, sinfo = self.findCaller(stack_info)
TypeError: findCaller() takes 1 positional argument but 2 were given
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/lib/python3.6/logging/__init__.py", line 1430, in _log
    fn, lno, func, sinfo = self.findCaller(stack_info)
TypeError: findCaller() takes 1 positional argument but 2 were given

[dirk-thomas]

@kartikmohta Thank you for the fix.

@asmodehn FYI

[paulbovbel]

FYI this is currently breaking ros1_bridge message generation, would kindly request a tagged release.

[dirk-thomas]

A new release will be made as soon as the pending logging regression has been fixed: see #1141.

[dirk-thomas]

The "broken" version should only be in the testing repo. You should be ok if you use the version available from the main repo.

[paulbovbel]

Thanks!