Update go-swagger libraries to the latest version and update to go modules

[bcomnes]

This PR turned into a mess. It does a few things:

Fix the missing consumer errors

The go-swagger runtime crashed on plain/html content types. This was causing problems in the buildbot, so the first step to address that was to update the go-swagger runtime libs to get the following fix:

• Generated client doesn't have "text/html" consumer go-openapi/runtime#106
• go-openapi/runtime@17da9ad

Update go-swagger to v0.18.0 from 94927f8c9742791a9aa46c6c3965f0a37025f41d

Fix the failing tests

After updating the go-swagger libraries, this test started failing:

open-api/go/porcelain/http/http_test.go

Lines 146 to 179 in 6aaaf6f

	func TestRetryableTransport_POST(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
	rw.WriteHeader(http.StatusCreated)
	rw.Write([]byte("test result"))
	}))
	defer server.Close()
	rwrtr := runtime.ClientRequestWriterFunc(func(req runtime.ClientRequest, _ strfmt.Registry) error {
	return req.SetBodyParam("test result")
	})
	hu, _ := url.Parse(server.URL)
	rt := NewRetryableTransport(httptransport.New(hu.Host, "/", []string{"http"}), 2)
	result, err := rt.Submit(&runtime.ClientOperation{
	ID: "createSite",
	Method: "POST",
	PathPattern: "/",
	Params: rwrtr,
	Reader: runtime.ClientResponseReaderFunc(func(response runtime.ClientResponse, consumer runtime.Consumer) (interface{}, error) {
	if response.Code() == 201 {
	var result string
	if err := consumer.Consume(response.Body(), &result); err != nil {
	return nil, err
	}
	return result, nil
	}
	return nil, errors.New("Generic error")
	}),
	})
	require.NoError(t, err)
	actual := result.(string)
	require.EqualValues(t, "test result", actual)

The error was the following:

Post http://127.0.0.1:41076/: http: ContentLength=14 with Body length 28

This comes from deep within the http request client, and happens when the body exceeds the content length of the req.ContentLength property.

https://github.com/golang/go/blob/61170f85e62f1326d42c4dbd8aa17ab4a1305a87/src/net/http/transfer.go#L387-L389

Rolling back to [email protected] from [email protected] makes the test pass again, but we should really confirm retry's with a body work.

Whats happening is:

• In the newer autorest versions, it calls rr.req.GetBody()

https://github.com/Azure/go-autorest/blob/1f7cd6cfe0adea687ad44a512dfe76140f804318/autorest/retriablerequest_1.8.go#L47-L53

• This doubles the size of the body in the req object for some reason. I haven't dug into why that is yet.
• For comparison: here is the new implementation of GetBody we are stuck with for now that seems to double the size body's size:

https://github.com/go-openapi/runtime/blob/9c75b2b632f58f9cb20e0767a724d5ebc37c2047/client/request.go#L209-L220

• Here is the old implementation of GetBody

https://github.com/go-openapi/runtime/blob/94927f8c9742791a9aa46c6c3965f0a37025f41d/client/request.go#L249-L254

• For comparison here are the two other strategies:

https://github.com/Azure/go-autorest/blob/1f7cd6cfe0adea687ad44a512dfe76140f804318/autorest/retriablerequest_1.7.go

• (this is the version we effectively rolled back too)

https://github.com/Azure/go-autorest/blob/1f7cd6cfe0adea687ad44a512dfe76140f804318/autorest/retriablerequest.go

Port over to go-modules

I simultaneously tried to move the go module over to its own repo https://github.com/netlify/go-client/tree/open-api but that is still being discussed: netlify/go-client#17

I wanted to get that work out asap since the buildbot is already on go-modules, so I ported that work into this PR.

Add test to cover no consumer errors

Add a tests to verify the client doesn't error out when it receives an html or text response.

Closes #122
Closes netlify/buildbot#362

[bcomnes]

Same error as #147, but with the new toolchain.

[bcomnes]

What's left now is to write some retriable tests with a body.

[bcomnes]

Ok, end of the day here for me, for tomorrow, I think its the interaction between:

• GetBody implementation in go-swagger https://github.com/go-openapi/runtime/blob/9c75b2b632f58f9cb20e0767a724d5ebc37c2047/client/request.go#L209-L220
• This part of the prepare() method in autorest: https://github.com/Azure/go-autorest/blob/1f7cd6cfe0adea687ad44a512dfe76140f804318/autorest/retriablerequest_1.8.go#L47-L54

[bcomnes]

Adding a replay test with the pinned version of autorest seems to work, so thats promising.

[bcomnes]

The docs changes here are still a wip.

[bcomnes]

Added a test to confirm we no longer will get the no-consumer error when we get an unexpected content type.

[calavera]

LGTM