Add better provider verification output

[bmarini]

This enables you to write your provider verification tests like this:

res, err := pact.VerifyProvider(types.VerifyRequest{
	ProviderBaseURL: "baseurl",
	PactURLs:        []string{"url1.json","url2.json"},
})
if err != nil {
	t.Fatal(err)
}
for _, ex := range res.Examples {
	if ex.Status != "passed" {
		t.Errorf("%s\n%s\n", ex.FullDescription, ex.Exception.Message)
	}
}

Changes

The main change is to func (p PactClient) VerifyProvider(request types.VerifyRequest, reply *types.ProviderVerifierResponse) error. The reply type is specific to the JSON output of the pact-provider-verifier binary. Also, I've changed the semantics of the error a bit. If a valid JSON response from the binary can be parsed, there will be no error. Otherwise, there will be an error, and it will include both stderr and stdout from the binary.

Notes

In doing this, I realized it would be pretty easy to repurpose the daemon package to remove the rpc layer and use it directly to execute the external ruby binaries. That could be a first step in solving #31

[bmarini]

I'll be sure to update docs and examples and readme if these changes are given the green light.

[bmarini]

This func is the only real addition for all these example tests. Everything else was just converting spaces to tabs.

[mefellows]

Thanks - weird I never picked this up!

[mefellows]

This looks great, I'll review today!

[mefellows]

In doing this, I realized it would be pretty easy to repurpose the daemon package to remove the rpc layer and use it directly to execute the external ruby binaries. That could be a first step in solving #31

Yep, the benefit of the current daemon approach is that the pact binaries are known to be co-located with the daemon. The challenges with removing the daemon, is that we need another way of getting the pact binaries onto the PATH, and then keeping them up to date. But agreed, it is the first step (FWIW this was always the plan).