Improved handling of missing param error and usage.

boto/roboto/awsqueryrequest.py

@@ -269,7 +269,17 @@ def process_args(self, **args):
             if python_name in self.args:
                 del self.connection_args[python_name]
         if required:
-            raise RequiredParamError(required)
+            l = []
+            for p in self.Params+self.Args:
+                if p.name in required:
+                    if p.short_name and p.long_name:
+                        l.append('(%s, %s)' % (p.optparse_short_name,
+                                               p.optparse_long_name))
+                    elif p.short_name:
+                        l.append('(%s)' % p.optparse_short_name)
+                    else:
+                        l.append('(%s)' % p.optparse_long_name)
+            raise RequiredParamError(','.join(l))
         boto.log.debug('request_params: %s' % self.request_params)
         self.process_markers(self.Response)
 
@@ -353,8 +363,15 @@ def process_standard_options(self, options, args, d):
         sys.excepthook = boto_except_hook(options.debugger,
                                           options.debug)
 
+    def get_usage(self):
+        s = 'usage: %prog [options] '
+        l = [ a.long_name for a in self.Args ]
+        s += ' '.join(l)
+        return s
+
     def build_cli_parser(self):
-        self.parser = optparse.OptionParser(description=self.Description)
+        self.parser = optparse.OptionParser(description=self.Description
+                                            usage=self.get_usage())
         self.add_standard_options()
         for param in self.Params:
             ptype = action = choices = None