refactor(PipeRegistry): improve error messages

Closes #1504

modules/angular2/src/change_detection/pipes/pipe_registry.js

@@ -15,16 +15,16 @@ export class PipeRegistry {
   get(type:string, obj, cdRef:ChangeDetectorRef):Pipe {
     var listOfConfigs = this.config[type];
     if (isBlank(listOfConfigs)) {
-      throw new BaseException(`Cannot find a pipe for type '${type}' object '${obj}'`);
+      throw new BaseException(`Cannot find '${type}' pipe supporting object '${obj}'`);
     }
 
     var matchingConfig = ListWrapper.find(listOfConfigs,
       (pipeConfig) => pipeConfig.supports(obj));
 
     if (isBlank(matchingConfig)) {
-      throw new BaseException(`Cannot find a pipe for type '${type}' object '${obj}'`);
+      throw new BaseException(`Cannot find '${type}' pipe supporting object '${obj}'`);
     }
 
     return matchingConfig.create(cdRef);
   }
-}
+}

modules/angular2/test/change_detection/pipes/pipe_registry_spec.js

@@ -22,7 +22,7 @@ export function main() {
     it("should throw when no matching type", () => {
       var r = new PipeRegistry({});
       expect(() => r.get("unknown", "some object", null)).toThrowError(
-        `Cannot find a pipe for type 'unknown' object 'some object'`
+        `Cannot find 'unknown' pipe supporting object 'some object'`
       );
     });
 
@@ -32,7 +32,7 @@ export function main() {
       });
 
       expect(() => r.get("type", "some object", null)).toThrowError(
-        `Cannot find a pipe for type 'type' object 'some object'`
+        `Cannot find 'type' pipe supporting object 'some object'`
       );
     });
   });
@@ -54,4 +54,4 @@ class PipeFactory {
   create(cdRef):Pipe {
     return this.pipe;
   }
-}
+}