Expose RequestErrorFromOauthError() for public consumption (#24)

* Reformat

[#167636840]

Signed-off-by: Andrew Wittrock <awittrock@pivotal.io>
Co-authored-by: Andrew Wittrock <awittrock@pivotal.io>

* Return RetrieveError in passwordcredentials

To match error behavior of golang oauth2 package

[#167636840]

Signed-off-by: Andrew Wittrock <awittrock@pivotal.io>
Co-authored-by: Andrew Wittrock <awittrock@pivotal.io>

api.go

@@ -213,7 +213,10 @@ func (a *API) validatePasswordCredentials() error {
 		EndpointParams: v,
 	}
 	a.passwordCredentialsConfig = c
-	a.AuthenticatedClient = c.Client(context.WithValue(context.Background(), oauth2.HTTPClient, a.UnauthenticatedClient))
+	a.AuthenticatedClient = c.Client(context.WithValue(
+		context.Background(),
+		oauth2.HTTPClient,
+		a.UnauthenticatedClient))
 	return a.ensureTransports()
 }
 

passwordcredentials/passwordcredentials.go

@@ -52,7 +52,10 @@ func retrieveToken(ctx context.Context, ClientID, ClientSecret, TokenURL string,
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}
 	if code := r.StatusCode; code < 200 || code > 299 {
-		return nil, fmt.Errorf("oauth2: cannot fetch token: %v\nResponse: %s", r.Status, body)
+		return nil, &oauth2.RetrieveError{
+			Response: r,
+			Body:     body,
+		}
 	}
 
 	var token *internalToken