Changed the behavior so that if a searcher rejects,

then the thenable returned by `atom.workspace.scan()` rejects.

spec/workspace-spec.coffee

@@ -1014,12 +1014,12 @@ describe "Workspace", ->
             cancelableSearch = atom.workspace.scan /aaaa/, ->
             fakeSearch.hoistedReject()
 
-            resultOfPromiseSearch = null
+            didReject = false
             waitsForPromise ->
-              cancelableSearch.then (promiseResult) -> resultOfPromiseSearch = promiseResult
+              cancelableSearch.catch -> didReject = true
 
             runs ->
-              expect(resultOfPromiseSearch).toBe('cancelled')
+              expect(didReject).toBe(true)
 
   describe "::replace(regex, replacementText, paths, iterator)", ->
     [filePath, commentFilePath, sampleContent, sampleCommentContent] = []

src/workspace.coffee

@@ -874,15 +874,18 @@ class Workspace extends Model
     # with the existing behavior, instead of cancel() rejecting the promise, it should
     # resolve it with the special value 'cancelled'. At least the built-in find-and-replace
     # package relies on this behavior.
+    isCancelled = false
     cancellablePromise = new Promise (resolve, reject) ->
       onSuccess = ->
         resolve(null)
-        return
       onFailure = ->
-        resolve('cancelled')
-        return
+        if isCancelled
+          resolve('cancelled')
+        else
+          reject()
       searchPromise.then(onSuccess, onFailure)
     cancellablePromise.cancel = ->
+      isCancelled = true
       # Note that cancelling all (or actually, any) of the members of allSearches
       # will cause searchPromise to reject, which will cause cancellablePromise to resolve
       # in the desired way.