[Validator] Use Pathname instead of File

lib/cocoapods/validator.rb

@@ -247,7 +247,7 @@ module Pod
     #
     def dot_swift_version
       swift_version_path = file.dirname + '.swift-version'
-      File.read(swift_version_path) if File.exist?(swift_version_path)
+      swift_version_path.read if swift_version_path.exist?
     end
 
     #-------------------------------------------------------------------------#

spec/unit/validator_spec.rb

@@ -835,18 +835,14 @@ module Pod
       describe '#dot_swift_version' do
         it 'looks for a .swift-version file' do
           validator = test_swiftpod
-          File.expects(:exist?).with do |arg|
-            arg.basename.to_s == '.swift-version'
-          end
+          Pathname.any_instance.expects(:exist?)
           validator.dot_swift_version
         end
 
         it 'uses the .swift-version file if present' do
           validator = test_swiftpod
-          File.stubs(:exist?).returns(true)
-          File.expects(:read).with do |arg|
-            arg.basename.to_s == '.swift-version'
-          end.returns('1.0')
+          Pathname.any_instance.stubs(:exist?).returns(true)
+          Pathname.any_instance.expects(:read).returns('1.0')
           validator.dot_swift_version.should == '1.0'
         end
       end