1) `Popen.communicate()` expects `bytes` (a raw, binary string) if `stdout`/`stderr` are open in binary mode but is given output from `json.loads()` which is str (an abstract unicode string). Encoding the `str` object into `bytes` using UTF-8 encoding fixes that.
2) `REPORT_FILE` gets opened in binary mode which means that functions like `write()` expect `bytes`. We're giving them `str` which results in an error. Changed mode to text solves the problem.
