This spec is a derivative of spec added with the original issue #324, which introduced the use of `Gem.default_exec_format % 'bundle'`.  
I personally have never encountered a situation, where `bundle` command is suffixed or prefixed, 
but since #324 was created, I assume there exist an environment, where `bundle` command is suffixed or prefixed. 
Under such environment, I am expecting `Gem.bin_path` to return a path with prefix and/or suffix.