Tidy up pinout a little:

Ensure all error messages are printed on stderr instead of stdout; make
sure all errors formatted the same and that argparse's default exit
codes are followed

gpiozero/cli/pinout.py

@@ -10,57 +10,56 @@ from __future__ import unicode_literals, absolute_import, print_function, divisi
 import argparse
 import sys
 
-from gpiozero import *
+from gpiozero import pi_info
 
 
-def parse_args(args):
-    parser = argparse.ArgumentParser(
-        description=__doc__
-    )
+class PinoutTool(object):
+    def __init__(self):
+        self.parser = argparse.ArgumentParser(
+            description=__doc__
+        )
+        self.parser.add_argument(
+            '-r', '--revision',
+            dest='revision',
+            default='',
+            help='RPi revision. Default is to autodetect revision of current device'
+        )
+        self.parser.add_argument(
+            '-c', '--color',
+            action="store_true",
+            default=None,
+            help='Force colored output (by default, the output will include ANSI'
+            'color codes if run in a color-capable terminal). See also --monochrome'
+        )
+        self.parser.add_argument(
+            '-m', '--monochrome',
+            dest='color',
+            action='store_false',
+            help='Force monochrome output. See also --color'
+        )
 
-    parser.add_argument(
-        '-r', '--revision',
-        dest='revision',
-        default='',
-        help='RPi revision. Default is to autodetect revision of current device'
-    )
-
-    parser.add_argument(
-        '-c', '--color',
-        action="store_true",
-        default=None,
-        help='Force colored output (by default, the output will include ANSI'
-        'color codes if run in a color-capable terminal). See also --monochrome'
-    )
-
-    parser.add_argument(
-        '-m', '--monochrome',
-        dest='color',
-        action='store_false',
-        help='Force monochrome output. See also --color'
-    )
-
-    try:
-        args = parser.parse_args(args)
-    except argparse.ArgumentError as ex:
-        print('Error parsing arguments.')
-        parser.error(str(ex.message))
-        sys.exit(1)
-    return args
-
-
-def main():
-    args = parse_args(sys.argv[1:])
-
-    if args.revision == '':
+    def __call__(self, args=None):
+        if args is None:
+            args = sys.argv[1:]
         try:
-            pi_info().pprint(color=args.color)
-        except IOError:
-            print('This device is not a Raspberry Pi')
-            sys.exit(1)
-    else:
-        pi_info(args.revision).pprint(color=args.color)
+            return self.main(self.parser.parse_args(args)) or 0
+        except argparse.ArgumentError as e:
+            # argparse errors are already nicely formatted, print to stderr and
+            # exit with code 2
+            raise e
+        except Exception as e:
+            # Output anything else nicely formatted on stderr and exit code 1
+            self.parser.exit(1, '{prog}: error: {message}\n'.format(
+                prog=self.parser.prog, message=e))
+
+    def main(self, args):
+        if args.revision == '':
+            try:
+                pi_info().pprint(color=args.color)
+            except IOError:
+                raise IOError('This device is not a Raspberry Pi')
+        else:
+            pi_info(args.revision).pprint(color=args.color)
 
 
-if __name__ == '__main__':
-    main()
+main = PinoutTool()