    # File lib/compass/commands/project_base.rb, line 56
          def assert_project_directory_exists!
            if File.exists?(project_directory) && !File.directory?(project_directory)
              raise Compass::FilesystemConflict.new("#{project_directory} is not a directory.")
            elsif !File.directory?(project_directory)
              raise Compass::Error.new("#{project_directory} does not exist.")
            end
          end