No more NotIdentifiedByImageMagick errors if IM is not in the path. Give a real error.

Based on a commit by Henrik N <henrik@nyh.se>

lib/paperclip.rb

@@ -113,6 +113,10 @@ module Paperclip
       Paperclip.log(command) if Paperclip.options[:log_command]
 
       output = `#{command}`
+
+      if $?.exitstatus == 127
+        raise CommandNotFoundError
+      end
       unless expected_outcodes.include?($?.exitstatus)
         raise PaperclipCommandLineError,
           "Error while running #{cmd}. Expected return code to be #{expected_outcodes.join(", ")} but was #{$?.exitstatus}",
@@ -167,7 +171,7 @@ module Paperclip
   class PaperclipError < StandardError #:nodoc:
   end
 
-  class PaperclipCommandLineError < StandardError #:nodoc:
+  class PaperclipCommandLineError < PaperclipError #:nodoc:
     attr_accessor :output
     def initialize(msg = nil, output = nil)
       super(msg)
@@ -175,9 +179,12 @@ module Paperclip
     end
   end
 
+  class CommandNotFoundError < PaperclipError
+  end
+
   class NotIdentifiedByImageMagickError < PaperclipError #:nodoc:
   end
-  
+
   class InfiniteInterpolationError < PaperclipError #:nodoc:
   end
 

test/paperclip_test.rb

@@ -62,6 +62,20 @@ class PaperclipTest < Test::Unit::TestCase
     end
   end
 
+  context "Calling Paperclip.run when the command is not found" do
+    should "tell you the command isn't there" do
+      begin
+        assert_raises(Paperclip::CommandNotFoundError) do
+          `ruby -e 'exit 127'` # Stub $?.exitstatus to be 127, i.e. Command Not Found.
+          Paperclip.stubs(:"`").returns("")
+          Paperclip.run("command")
+        end
+      ensure
+        `ruby -e 'exit 0'` # Unstub $?.exitstatus
+      end
+    end
+  end
+
   should "prevent dangerous characters in the command via quoting" do
     Paperclip.options[:image_magick_path] = nil
     Paperclip.options[:command_path]      = nil