Suppress warnings globally

[gipert]

If warnings show up (and this is often the case), they clutter the Snakemake console output and make it unreadable. We should fix issues highlighted by warnings, rather than suppressing them, but sometimes we just want to suppress them. It would be useful to set a list of warnings to be ignored in the config file.

[ggmarshall]

can we compile a list here of the common ones