bitbake: bitbake: Convert to python 3

Various misc changes to convert bitbake to python3 which don't warrant
separation into separate commits.

(Bitbake rev: d0f904d407f57998419bd9c305ce53e5eaa36b24)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/bin/bitbake-layers

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # This script has subcommands which operate against your bitbake layers, either
 # displaying useful information, or acting against them.
@@ -48,7 +48,6 @@ def logger_create(name, output=sys.stderr):
     logger.setLevel(logging.INFO)
     return logger
 
-
 def logger_setup_color(logger, color='auto'):
     from bb.msg import BBLogFormatter
     console = logging.StreamHandler(sys.stdout)
@@ -61,7 +60,6 @@ def logger_setup_color(logger, color='auto'):
 
 logger = logger_create('bitbake-layers', sys.stdout)
 
-
 def main():
     parser = argparse.ArgumentParser(
         description="BitBake layers utility",
@@ -78,6 +76,7 @@ def main():
     parser.add_argument('-h', '--help', action='help', default=argparse.SUPPRESS,
                         help='show this help message and exit')
     subparsers = parser.add_subparsers(title='subcommands', metavar='<subcommand>')
+    subparsers.required = True
 
     if global_args.debug:
         logger.setLevel(logging.DEBUG)