Avoid duplicate error messages from verification. (#557)
Avoid duplicate error messages from verification. (#557)

As reported by Emily, currently users see this:

    "coin.pact:212:10:Warning: Analysis doesn't support this construct yet"
    coin.pact:212:10:Warning: Analysis doesn't support this construct yet

This is due to (1) showing a message on `stderr` and (2) returning a
string result from the call to `verify`.

In this change we follow the lead of `typecheck` which shows a different
message in the two contexts.
kadena-io/pact,kadena-io/pact,kadena-io/pact,kadena-io/pact