permissions check, more db helper functions

contest/checks.py

@@ -0,0 +1,15 @@
+from discord.ext import commands
+
+
+def check_permissions(ctx, perms, *, check=all):
+    resolved = ctx.channel.permissions_for(ctx.author)
+    return check(getattr(resolved, name, None) == value for name, value in perms.items())
+
+
+def privileged():
+    def predicate(ctx):
+        return (ctx.guild is not None and ctx.guild.owner_id == ctx.author.id) \
+               or check_permissions(ctx, {'manage_guild': True}) \
+               or check_permissions(ctx, {'administrator': True})
+
+    return commands.check(predicate)