That particular error that you added could be triggered if the binary file
you're reading in was corrupted somehow, or perhaps if the compiler changed
and we removed an ImportMethod (for example if we got rid of 'Hiding'
somehow) and we tried to read an old version of the file. I think your
message is OK - all we can really say is that it's an invalid ImportMethod
in the end. Hopefully the compiler version check that I added will catch
most of this before getting to this point anyway as long as we update the
Elm version with releases that cause changes in the elmi files.