prior to this change, many of the functions in the ExecTx callback would
wrap the error before returning it. this made it impossible to check
for the error code.
instead, the error wrapping has been moved to be external to the
`ExecTx` callback, so that the error code can be checked and
serialization failures can be retried.
this failed on my machine due to the unexported 'loc' field of the time
structure - it was nil in one and set to a ton of tiemzone data in the
other. instead let's just compare the unix timestamp value and zero it
out for the struct comparison.
Alex Suraci