Python3: fix NVDA's logging infrastructure

[michaelDCurran]

Link to issue number:

None.

Summary of the issue:

In Python3: several issues cause NVDA's logging to fail:

• NVDA makes use of logging._levelNames which no longer exists in Python3.
• When NvDA calculates a code path when logging, it accesses a function's code object via its func_code property. In Python3 this is now __code__.
• As strings are now unicode, and files that are opened in text mode deal in unicode, NVDA's logHandler.FileHandler no longer works.

Description of how this pull request fixes the issue:

• No longer use logging._levelNames, rather use logging.getLevelName.
• Changed logHandler.getCodePath to use __code__ instead of func_code.
• logHandler.FileHandler now inherits from logging.Filehandler rather than the lower-level StreamHandler, and no longer converts to utf8 before writing. Rather the File object itself handles the utf8 encoding.

Testing performed:

Started NVDA under Python3. Info messages and tracebacks were successfully logged.

Known issues with pull request:

None.

Change log entry:

None.

Section: New features, Changes, Bug fixes

[LeonarddeR]

Just a few comments

[feerrenrut]

There are still a few references to func_code in this file, could you check the rest of the code-base while you are at it? Could you also check for logging._levelNames in the rest of the code-base too?

Note, there are a few review comments from Leonard as well.

[michaelDCurran]

I had previously grepped for any other uses of _levelNames and corrected them. There are none left.

[michaelDCurran]

I have addressed review comments. Though didn't change the 'is' to an isinstance as this was existing code and I'm trying to avoid changing anything not necessary to change due to Python 3.