[Utils] Finish and Refactor Predicate Utility (#2169)

* Uses classmethods to create predicates
* Classmethods allow using a combination of different parameters to describe context
* Some predicates assign a captured `result` to the predicate object on success
* Added `ReactionPredicate` equivalent to `MessagePredicate`
* Added `utils.menus.start_adding_reactions`, a non-blocking method for adding reactions asynchronously
* Added documentation
* Uses these new utils throughout the core bot
Happened to also find some bugs in places, and places where we were waiting for events without catching `asyncio.TimeoutError`

Signed-off-by: Toby Harradine <tobyharradine@gmail.com>

redbot/cogs/reports/reports.py

@@ -11,6 +11,7 @@ from redbot.core.utils.chat_formatting import pagify, box
 from redbot.core.utils.antispam import AntiSpam
 from redbot.core.bot import Red
 from redbot.core.i18n import Translator, cog_i18n
+from redbot.core.utils.predicates import MessagePredicate
 from redbot.core.utils.tunnel import Tunnel
 
 
@@ -136,13 +137,14 @@ class Reports(commands.Cog):
         output += "\n{}".format(prompt)
 
         for page in pagify(output, delims=["\n"]):
-            dm = await author.send(box(page))
-
-        def pred(m):
-            return m.author == author and m.channel == dm.channel
+            await author.send(box(page))
 
         try:
-            message = await self.bot.wait_for("message", check=pred, timeout=45)
+            message = await self.bot.wait_for(
+                "message",
+                check=MessagePredicate.same_context(channel=author.dm_channel, user=author),
+                timeout=45,
+            )
         except asyncio.TimeoutError:
             await author.send(_("You took too long to select. Try again later."))
             return None
@@ -247,7 +249,7 @@ class Reports(commands.Cog):
             val = await self.send_report(_m, guild)
         else:
             try:
-                dm = await author.send(
+                await author.send(
                     _(
                         "Please respond to this message with your Report."
                         "\nYour report should be a single message"
@@ -256,11 +258,12 @@ class Reports(commands.Cog):
             except discord.Forbidden:
                 return await ctx.send(_("This requires DMs enabled."))
 
-            def pred(m):
-                return m.author == author and m.channel == dm.channel
-
             try:
-                message = await self.bot.wait_for("message", check=pred, timeout=180)
+                message = await self.bot.wait_for(
+                    "message",
+                    check=MessagePredicate.same_context(ctx, channel=author.dm_channel),
+                    timeout=180,
+                )
             except asyncio.TimeoutError:
                 return await author.send(_("You took too long. Try again later."))
             else: