options.py: o.fatal(): print error after, not before, usage message.

git prints the error *before* the usage message, but the more I play with
it, the more I'm annoyed by that behaviour.  The usage message can be pretty
long, and the error gots lost way above the usage message.  The most
important thing *is* the error, so let's print it last.

Signed-off-by: Avery Pennarun <apenwarr@gmail.com>

lib/bup/options.py

@@ -184,14 +184,15 @@ def _gen_usage(self):
     def usage(self, msg=""):
         """Print usage string to stderr and abort."""
         sys.stderr.write(self._usagestr)
+        if msg:
+            sys.stderr.write(msg)
         e = self._onabort and self._onabort(msg) or None
         if e:
             raise e
 
-    def fatal(self, s):
+    def fatal(self, msg):
         """Print an error message to stderr and abort with usage string."""
-        msg = 'error: %s\n' % s
-        sys.stderr.write(msg)
+        msg = '\nerror: %s\n' % msg
         return self.usage(msg)
 
     def parse(self, args):

main.py

@@ -29,7 +29,7 @@
 # after running 'bup newliner', the tty_width() ioctl won't work anymore
 os.environ['WIDTH'] = str(tty_width())
 
-def usage():
+def usage(msg=""):
     log('Usage: bup [-?|--help] [-d BUP_DIR] [--debug] [--profile] '
         '<command> [options...]\n\n')
     common = dict(
@@ -62,6 +62,8 @@ def usage():
 
     log("See 'bup help COMMAND' for more information on " +
         "a specific command.\n")
+    if msg:
+        log("\n%s\n" % msg)
     sys.exit(99)
 
 
@@ -73,8 +75,7 @@ def usage():
     optspec = ['help', 'version', 'debug', 'profile', 'bup-dir=']
     global_args, subcmd = getopt.getopt(argv[1:], '?VDd:', optspec)
 except getopt.GetoptError, ex:
-    log('error: ' + ex.msg + '\n')
-    usage()
+    usage('error: %s' % ex.msg)
 
 help_requested = None
 dest_dir = None
@@ -93,8 +94,7 @@ def usage():
     elif opt[0] in ['-d', '--bup-dir']:
         dest_dir = opt[1]
     else:
-        log('error: unexpected option "%s"\n' % opt[0])
-        usage()
+        usage('error: unexpected option "%s"' % opt[0])
 
 if len(subcmd) == 0:
     if help_requested:
@@ -124,8 +124,7 @@ def subpath(s):
 
 subcmd[0] = subpath(subcmd_name)
 if not os.path.exists(subcmd[0]):
-    log('error: unknown command "%s"\n' % subcmd_name)
-    usage()
+    usage('error: unknown command "%s"' % subcmd_name)
 
 already_fixed = atoi(os.environ.get('BUP_FORCE_TTY'))
 if subcmd_name in ['mux', 'ftp', 'help']: