py3: make sure opts are passed and used correctly in help command

py3: make sure opts are passed and used correctly in help command

opts are converted back to bytes in help.help_() where they are used.
Before that it's ensured that we have a bytes value for keep variable.

--- a/mercurial/commands.py	Wed May 03 15:25:06 2017 +0530
+++ b/mercurial/commands.py	Fri Apr 28 00:49:30 2017 +0530
@@ -2759,7 +2759,7 @@
     Returns 0 if successful.
     """
 
-    keep = opts.get('system') or []
+    keep = opts.get(r'system') or []
     if len(keep) == 0:
         if pycompat.sysplatform.startswith('win'):
             keep.append('windows')

--- a/mercurial/help.py	Wed May 03 15:25:06 2017 +0530
+++ b/mercurial/help.py	Fri Apr 28 00:49:30 2017 +0530
@@ -23,6 +23,7 @@
     filemerge,
     fileset,
     minirst,
+    pycompat,
     revset,
     templatefilters,
     templatekw,
@@ -304,6 +305,7 @@
     '''
 
     from . import commands # avoid cycle
+    opts = pycompat.byteskwargs(opts)
 
     def helpcmd(name, subtopic=None):
         try: