Werkzeug 0.15.0 causes TensorBoard to log HTTP requests at INFO

[nfelt]

Updating Werkzeug to today's 0.15.0 release (from 0.14.1) changes the behavior so that it starts logging all HTTP requests at level INFO by default, even though TensorBoard is supposed to only log WARNING and above.

Looking at the logging code, it seems like pallets/werkzeug#1407 is the relevant change. It makes it so that Werkzeug's logging is set to log at INFO unconditionally now if you don't explicitly set it, whereas before this only happened if there was no root handler set and thus Werkzeug set up its own log handler. Presumably we are setting up our own log handler via absl.logging, so before the Werkzeug logger level remained at logging.NOTSET which causes it to inherit the root logger level setting (which TensorBoard sets to WARNING by default).

Unfortunately, this change makes it difficult for us to configure Werkzeug to reliably inherit the root logger level as its effective level, which means that it's hard to have our --verbosity flag control both tensorboard and werkzeug loggers as it has been doing.

I have some ideas here that I can look into.