Multiple Exceptions, use a CompositeException?

[oxinabox]

Right now if there are multiple errors, only one is thrown.
Julia has a CompositeException type that wraps many execeptions, it is intended for use with tasks, but we could use it for this, or we could make another similar type that wraps many.
That seems cleaner than just losing all but the first as we currently do

EzXML.jl/src/error.jl

Line 79 in 8cc2855

@warn("caught $(length(XML_GLOBAL_ERROR_STACK)) errors; showing the first one")

In general getting a warning like this can be annouying since if we actually can recover from the error (via try-catch) then the end user never finds out what that warning is talking about.