add some nice methods to the exception object

lib/shell_whisperer.rb

@@ -3,7 +3,13 @@
 
 module ShellWhisperer
   class CommandFailed < StandardError
+    attr_reader :original_message, :original_command, :exit_code
+
     def initialize(cmd, result, exit_code)
+      @original_command = cmd
+      @original_message = result
+      @exit_code = exit_code
+
       super "Attempted to run #{cmd.inspect} but the shell reported error: " \
             "#{result.chomp.inspect} and exited with exit code #{exit_code}."
     end

spec/shell_whisperer_spec.rb

@@ -17,6 +17,20 @@
       it "should fail" do
         expect { subject }.to raise_error(ShellWhisperer::CommandFailed, /fafa/)
       end
+
+      it "should expose information about what went wrong" do
+        failed = false
+        begin
+          subject
+        rescue ShellWhisperer::CommandFailed => e
+          expect(e.original_command).to eq 'fafa'
+          expect(e.original_message).to match /fafa/
+          expect(e.exit_code).to eq 127
+          failed = true
+        end
+
+        expect(failed).to be true
+      end
     end
   end
 end