Code review comment for lp:~niemeyer/pyjuju/no-regex-option

This is modifying a global variable when a deprecated usage is found, but multiple formulas may be utilized in a single command (deploy with auto-resolve against the ppa, or --with syntax for example), and in that case deprecated usage by additional formulas would go un-logged. perhaps keying to config path in a class dict, or just yagni for now