Fix aiohttp/apache http2 bug in ?muf and ?fof2

For more info, https://github.com/aio-libs/aiohttp/issues/3904
It is not possible to fix it by bumping aiohttp since it is pinned by another
dependency.

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 
 ## [Unreleased]
+### Fixed
+- Issue where `?muf` and `?fof2` would fail with an aiohttp error.
 
 
 ## [2.7.5] - 2022-06-08

exts/propagation.py

@@ -33,7 +33,7 @@ class PropagationCog(commands.Cog):
     async def mufmap(self, ctx: commands.Context):
         """Shows a world map of the Maximum Usable Frequency (MUF)."""
         async with ctx.typing():
-            async with self.session.get(self.muf_url) as r:
+            async with self.session.get(self.muf_url, headers={"Connection": "Upgrade", "Upgrade": "http/1.1"}) as r:
                 svg = await r.read()
             out = BytesIO(cairosvg.svg2png(bytestring=svg))
             file = discord.File(out, "muf_map.png")
@@ -47,7 +47,7 @@ class PropagationCog(commands.Cog):
     async def fof2map(self, ctx: commands.Context):
         """Shows a world map of the Critical Frequency (foF2)."""
         async with ctx.typing():
-            async with self.session.get(self.fof2_url) as r:
+            async with self.session.get(self.fof2_url,  headers={"Connection": "Upgrade", "Upgrade": "http/1.1"}) as r:
                 svg = await r.read()
             out = BytesIO(cairosvg.svg2png(bytestring=svg))
             file = discord.File(out, "fof2_map.png")