Writing to a file when flash is full.

[ilikecake]

This may be beyond the scope of this library, but it appears that if you use the FileHandler, if the flash drive is full, the code will crash with an OSError: [Errno 28] No space left on device. I am considering the case where you have a bunch of messages being logged and you fill up the flash space completely. Should this error be handled by the logger?

[ilikecake]

I added a log rotation feature to the file handler: #56