[BUG] Rich loghandler raising exceptions when using pythonw

After switching to using the Rich log handler in an application it started raising 'NoneType' object has no attribute 'write' exceptions, however, this would only happen when the debugger was not connected and running under pythonw (the special windows version that does not create a console window, used for GUI applications).

On a hunch I checked the implementation of Pythons builtin log handler (that we had been using previously) and found the following line in the Handler.handleError:

if raiseExceptions and sys.stderr: # see issue 13807

This confirmed my hunch, when using pythonw both sys.stdout and sys.stderr are None. The Rich logger doesn’t appear to have an exception handler catching all exceptions being generated when rending log output and deferring to the handleError method.

To Reproduce

Running this with Python will produce the expected log message, running with pythonw will generate the error.txt file with the missing attribute exception.

import logging
from rich.logging import RichHandler

logging.basicConfig(handlers=[RichHandler()], level=logging.INFO)

try:
    logging.info("My amazing info message")
except Exception as ex:
    with open("error.txt", "w") as f_out:
        print(str(ex), file=f_out)

Platform This is a Windows-specific error

[willmcgugan]

Fix is in 10.13.0

[timsavage]

The emit method of logging.StreamHandler (ref https://github.com/python/cpython/blob/main/Lib/logging/__init__.py#L1103 ) has a try/except block that catches Exception and passes the record to Handler.handleError. The docstring for handleError states

This method should be called from handlers when an exception is encountered during an emit() call.

This was the pattern I followed in the PR associated with this issue.