[Cache] Handle the expected spec not being found

This prevents us from handing out locations from the deleted tmpdir

CHANGELOG.md

@@ -94,6 +94,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Samuel Giddins](https://github.com/segiddins)
   [#3719](https://github.com/CocoaPods/CocoaPods/issues/3719)
 
+* Attempting to specify a `git` source where a Podspec for the requested pod is
+  not found will have a more helpful error message.  
+  [Samuel Giddins](https://github.com/segiddins)
+
 
 ## 0.37.2
 

lib/cocoapods/downloader/cache.rb

@@ -151,6 +151,7 @@ module Pod
       def uncached_pod(request)
         in_tmpdir do |target|
           result, podspecs = download(request, target)
+          result.location = nil
 
           podspecs.each do |name, spec|
             destination = path_for_pod(request, :name => name, :params => result.checkout_options)

spec/unit/downloader/cache_spec.rb

@@ -99,6 +99,17 @@ module Pod
             @cache.expects(:uncached_pod).once
             @cache.download_pod(@unreleased_request)
           end
+
+          it 'does not return a location when there is no spec with the request name' do
+            @stub_download.call do
+              @spec.name = 'OrangeLib'
+              File.open('BananaLib.podspec.json', 'w') { |f| f << @spec.to_pretty_json }
+              @spec.source
+            end
+            result = @cache.download_pod(@unreleased_request)
+            result.location.should.be.nil
+            result.spec.should.be.nil
+          end
         end
       end