Fix python warnings about filehandles left open

[maartenboersma]

We don't like python warnings, so we run with export PYTHONWARNINGS=error.

This floods the console with warnings like this.

ResourceWarning: unclosed file <_io.TextIOWrapper name='sram_1r1w_64x46/sram_1r1w_64x46.log' mode='a' encoding='UTF-8'>
Exception ignored in: <_io.FileIO name='sram_1r1w_64x46/sram_1r1w_64x46.log' mode='ab' closefd=True>
Traceback (most recent call last):
  File "../src/OpenRAM/compiler/debug.py", line 62, in print_raw
    log(str)

I found the problem (re-opening a file over and over again, never closing it) and fixed them by closing the filehandle after use.

Side recommendation: don't write your own logger infrastructure ever again. Others did it for you

[mguthaus]

OpenRAM was originally written in Python 2.x before there even was a decent logger. Thanks for your issue.