mididings: drop

Doesn't support recent python3 versions that use `async` as a keyword.

```
  File "/build/source/mididings/units/call.py", line 36
    def __init__(self, function, async, cont):
                                 ^
SyntaxError: invalid syntax
```

pkgs/tools/audio/mididings/default.nix

@@ -1,38 +0,0 @@
-{ lib, python2Packages, fetchFromGitHub, pkg-config, glib, alsa-lib, libjack2  }:
-
-python2Packages.buildPythonApplication {
-  version = "2015-11-17";
-  pname = "mididings";
-
-  src = fetchFromGitHub {
-    owner = "dsacre";
-    repo = "mididings";
-    rev = "bbec99a8c878a2a7029e78e84fc736e4a68ed5a0";
-    sha256 = "1pdf5mib87zy7yjh9vpasja419h28wvgq6x5hw2hkm7bg9ds4p2m";
-  };
-
-  nativeBuildInputs = [ pkg-config ];
-  buildInputs = [ glib alsa-lib libjack2 python2Packages.boost ];
-  propagatedBuildInputs = with python2Packages; [ decorator ]
-    # for livedings
-    ++ [ tkinter pyliblo ]
-    # for mididings.extra
-    ++ [ dbus-python pyinotify ]
-    # to read/write standard MIDI files
-    ++ [ pysmf ]
-    # so mididings knows where to look for config files
-    ++ [ pyxdg ];
-
-  preBuild = with lib.versions; ''
-    substituteInPlace setup.py \
-      --replace boost_python "boost_python${major python2Packages.python.version}${minor python2Packages.python.version}"
-  '';
-
-  meta = with lib; {
-    description = "A MIDI router and processor based on Python, supporting ALSA and JACK MIDI";
-    homepage = "http://das.nasophon.de/mididings";
-    license = licenses.gpl2;
-    maintainers = [ ];
-    platforms = platforms.linux;
-  };
-}

pkgs/top-level/aliases.nix

@@ -591,6 +591,7 @@ mapAliases ({
   metamorphose2 = throw "metamorphose2 has been removed from nixpkgs, as it was stuck on python2."; # added 2022-01-12
   mcgrid = throw "mcgrid has been removed from nixpkgs, as it's not compatible with rivet 3"; # added 2020-05-23
   mcomix = throw "mcomix has been removed from nixpkgs, as it's unmaintained; try mcomix3 a Python 3 fork"; # added 2019-12-10, modified 2020-11-25
+  mididings = throw "mididings has been removed from nixpkgs as it doesn't support recent python3 versions and its upstream stopped maintaining it."; # added 2022-01-12
   mimms = throw "mimms has been removed from nixpkgs as the upstream project is stuck on python2."; # added 2022-01-01
   mirage = throw "mirage has been removed from nixpkgs, as it's unmaintained"; # added 2019-12-10
   minergate = throw "minergate has been removed from nixpkgs, because the package is unmaintained and the site has a bad reputation"; # added 2021-08-13

pkgs/top-level/all-packages.nix

@@ -3398,8 +3398,6 @@ with pkgs;
 
   midicsv = callPackage ../tools/audio/midicsv { };
 
-  mididings = callPackage ../tools/audio/mididings { };
-
   miniscript = callPackage ../applications/blockchains/miniscript { };
 
   miniserve = callPackage ../tools/misc/miniserve {