Fix RSpec::Core::RakeTask#failure_message.

`system` returns a boolean value to indicate success/failure,
but the use of `failure_message` was in a `rescue` block that
never got executed.  It appears this has been broken since
ea70e4e. Before that commit,
we used `Rake::FileUtilsExt#ruby`, which does indicate failure
by raising an error (and thus the `rescue` was correct). In
ea70e4e, we switched to using
`system` and the rescue was left in place but never got hit
anymore.

The lack of test coverage here is why we never noticed, so I
addressed that as well.

Author: myronmarston

Changelog.md

@@ -32,6 +32,8 @@ Bug Fixes:
 * Handle invalid UTF-8 strings within exception methods. (Benjamin Fleischer, #1760)
 * Fix Rake Task quoting of file names with quotes to work properly on
   Windows. (Myron Marston, #1887)
+* Fix `RSpec::Core::RakeTask#failure_message` so that it gets printed
+  when the task failed. (Myron Marston, #1905)
 
 ### 3.2.2 / 2015-03-11
 [Full Changelog](http://github.com/rspec/rspec-core/compare/v3.2.1...v3.2.2)

lib/rspec/core/rake_task.rb

@@ -63,16 +63,12 @@ def initialize(*args, &task_block)
       # @private
       def run_task(verbose)
         command = spec_command
+        puts command if verbose
 
-        begin
-          puts command if verbose
-          success = system(command)
-        rescue
-          puts failure_message if failure_message
-        end
-
-        return unless fail_on_error && !success
+        return if system(command)
+        puts failure_message if failure_message
 
+        return unless fail_on_error
         $stderr.puts "#{command} failed" if verbose
         exit $?.exitstatus
       end

spec/rspec/core/rake_task_spec.rb

@@ -80,6 +80,23 @@ def spec_command
       end
     end
 
+    context "when `failure_message` is configured" do
+      before do
+        allow(task).to receive(:exit)
+        task.failure_message = "Bad news"
+      end
+
+      it 'prints it if the RSpec run failed' do
+        task.ruby_opts = '-e "exit(1);" ;#'
+        expect { task.run_task false }.to output(/Bad news/).to_stdout
+      end
+
+      it 'does not print it if the RSpec run succeeded' do
+        task.ruby_opts = '-e "exit(0);" ;#'
+        expect { task.run_task false }.not_to output(/Bad/).to_stdout
+      end
+    end
+
     context 'with custom exit status' do
       def silence_output(&block)
         expect(&block).to output(anything).to_stdout.and output(anything).to_stderr