Fix frozen string literal issues

Gemfile

@@ -12,6 +12,6 @@ group :test, :default do
 end
 
 group :test do
-  gem "simplecov"
+  gem "simplecov", '~> 0.22.0'
   gem "codeclimate-test-reporter", "~> 1.0.0"
 end

lib/fog/aws/requests/lambda/create_event_source_mapping.rb

@@ -56,7 +56,7 @@ def create_event_source_mapping(params={})
           function = self.get_function_configuration('FunctionName' => function_name).body
 
           unless event_source_arn
-            message  = "ValidationException => "
+            message  = +"ValidationException => "
             message << "'eventSourceArn' cannot be blank"
             raise Fog::AWS::Lambda::Error, message
           end

lib/fog/aws/requests/lambda/create_function.rb

@@ -109,7 +109,7 @@ def create_function(params={})
           end
 
           if !function.empty?
-            message  = "ResourceConflictException => "
+            message  = +"ResourceConflictException => "
             message << "Function already exist: #{function_name}"
             raise Fog::AWS::Lambda::Error, message
           end

lib/fog/aws/requests/lambda/get_event_source_mapping.rb

@@ -33,7 +33,7 @@ def get_event_source_mapping(params={})
           mapping_id = params.delete('UUID')
 
           unless mapping = self.data[:event_source_mappings][mapping_id]
-            message  = 'ResourceNotFoundException => '
+            message  = +'ResourceNotFoundException => '
             message << 'The resource you requested does not exist.'
             raise Fog::AWS::Lambda::Error, message
           end

lib/fog/aws/requests/lambda/get_policy.rb

@@ -31,7 +31,7 @@ def get_policy(params={})
           statements   = self.data[:permissions][function_arn] || []
 
           if statements.empty?
-            message = "ResourceNotFoundException => "
+            message = +"ResourceNotFoundException => "
             message << "The resource you requested does not exist."
             raise Fog::AWS::Lambda::Error, message
           end

lib/fog/aws/requests/lambda/invoke.rb

@@ -46,7 +46,7 @@ def invoke(params={})
           response.body = ''
 
           unless function_id = params.delete('FunctionName')
-            message = 'AccessDeniedException => '
+            message = +'AccessDeniedException => '
             message << 'Unable to determine service/operation name to be authorized'
             raise Fog::AWS::Lambda::Error, message
           end
@@ -63,7 +63,7 @@ def invoke(params={})
           end
 
           if payload
-            message = "payload parameter is ignored since we are not really "
+            message = +"payload parameter is ignored since we are not really "
             message << "invoking a function [light_black](#{caller.first})[/]"
             Fog::Logger.warning message
           end

lib/fog/aws/requests/lambda/update_event_source_mapping.rb

@@ -47,7 +47,7 @@ def update_event_source_mapping(params={})
           mapping = self.data[:event_source_mappings][mapping_id]
 
           unless mapping
-            message  = 'ResourceNotFoundException => '
+            message  = +'ResourceNotFoundException => '
             message << 'The resource you requested does not exist.'
             raise Fog::AWS::Lambda::Error, message
           end

lib/fog/aws/requests/storage/acl_utils.rb

@@ -5,7 +5,7 @@ class Storage
 
       private
         def self.hash_to_acl(acl)
-          data =  "<AccessControlPolicy>\n"
+          data =  +"<AccessControlPolicy>\n"
 
           if acl['Owner'] && (acl['Owner']['ID'] || acl['Owner']['DisplayName'])
             data << "  <Owner>\n"

lib/fog/aws/requests/storage/cors_utils.rb

@@ -6,7 +6,7 @@ class Storage
       private
 
         def self.hash_to_cors(cors)
-          data =  "<CORSConfiguration>\n"
+          data =  +"<CORSConfiguration>\n"
 
           [cors['CORSConfiguration']].flatten.compact.each do |rule|
             data << "  <CORSRule>\n"

tests/requests/lambda/helper.rb

@@ -65,7 +65,7 @@ module Formats
       DELETE_EVENT_SOURCE_MAPPING = GET_EVENT_SOURCE_MAPPING
 
       def self.zip(data, filename='index.js')
-        data_io = Zip::OutputStream.write_buffer do |zio|
+        data_io = Zip::OutputStream.write_buffer(StringIO.new) do |zio|
           zio.put_next_entry(filename)
           zio.write(data)
         end

tests/requests/storage/object_tests.rb

@@ -36,7 +36,7 @@
     end
 
     tests("#get_object('#{@directory.identity}', 'fog_object', &block)").returns(lorem_file.read) do
-      data = ''
+      data = +''
       Fog::Storage[:aws].get_object(@directory.identity, 'fog_object') do |chunk, remaining_bytes, total_bytes|
         data << chunk
       end