Verified failure on installed 3.4.3, Win 7, with 3 rather than 1 error (all similar).
test_no_args_compiles_path (test.test_compileall.CommandLineTests) ... FAIL
test_no_args_respects_force_flag (test.test_compileall.CommandLineTests) ... FAIL
test_no_args_respects_quiet_flag (test.test_compileall.CommandLineTests) ... FAIL
test_pep3147_paths_doubleoptimize (test.test_compileall.CommandLineTests) ... ok

First traceback ends with
AssertionError: Process return code is 1, command line was: ['C:\\Programs\\Python34\\python.exe', '-X', 'faulthandler', '-S', '-m', 'compil
eall'], stderr follows:

followed by another ending with
  File "C:\Programs\Python34\lib\encodings\cp1252.py", line 19, in encode
    return codecs.charmap_encode(input,self.errors,encoding_table)[0]
UnicodeEncodeError: 'charmap' codec can't encode character '\U00011111' in position 38: character maps to <undefined>

Why is an astral char in the error message?

Will try patch.