An before the vowel said my English teacher

lib/cocoapods/installer.rb

@@ -192,7 +192,7 @@ module Pod
     # Ensures that the white-listed build configurations are known to prevent
     # silent typos.
     #
-    # @raise  If a unknown user configuration is found.
+    # @raise  If an unknown user configuration is found.
     #
     def validate_build_configurations
       whitelisted_configs = pod_targets.map do |target|

lib/cocoapods/validator.rb

@@ -529,7 +529,7 @@ module Pod
       output, status = _xcodebuild "#{command} 2>&1"
 
       unless status.success?
-        message = 'Returned a unsuccessful exit code.'
+        message = 'Returned an unsuccessful exit code.'
         message += ' You can use `--verbose` for more information.' unless config.verbose?
         error('xcodebuild', message)
       end

spec/unit/validator_spec.rb

@@ -370,7 +370,7 @@ module Pod
         validator.stubs(:_xcodebuild).returns(['Output', status])
         validator.validate
         first = validator.results.map(&:to_s).first
-        first.should.include '[xcodebuild] Returned a unsuccessful exit code'
+        first.should.include '[xcodebuild] Returned an unsuccessful exit code'
         validator.result_type.should == :error
       end