Dealing with rejected Mutations

[Josh Elser]

I remember hearing in passing at least once about the lack of insight 
into which mutation(s) out of a batch sent to a BatchWriter failed. I 
checked briefly, but I didn't find any docs that specifically talk about 
this.

Additionally, what are the failure causes? Can I see a 
MutationsRejectedException for some reason other than a failed 
Constraint or permissions issue? Is tserver failure handled implicitly 
by the WAL and/or BatchWriter implementation?

Thanks.