use tr to filter invalid characters, fix #1

Author: Windfarer

main.py

@@ -50,6 +50,8 @@ def cleanup(*args):
 
 DUMP_CMD = 'mysqldump -h {host} -P {port} -u {user} --password={password} {db} {table} ' \
            '--default-character-set=utf8 -X'.format(**config['mysql'])
+
+# For removing invalid characters in xml stream.
 REMOVE_INVALID_PIPE = r'tr -d "\00\01\02\03\04\05\06\07\10\13\14\16\17\20\21\22\23\24\25\26\27\30\31\32\33\34\35\36\37"'
 
 BINLOG_CFG = {key: config['mysql'][key] for key in ['host', 'port', 'user', 'password', 'db']}