Describe the bug
appimage-run currently depends on gst-plugins-base-0.10.36, which has been marked broken with d034a00. This is causing it to fail:

error: Package ‘gst-plugins-base-0.10.36’ in /nix/store/d6ccdwwij22dfkcpiy1asznli5n0fvyv-nixpkgs-20.09pre234801.1facbd61b17/nixpkgs/pkgs/development/libraries/gstreamer/legacy/gst-plugins-base/default.nix:55 is marked as broken, refusing to evaluate.

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowBroken = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowBroken = true; }
to ~/.config/nixpkgs/config.nix.

(use '--show-trace' to show detailed location information)

To Reproduce
Steps to reproduce the behavior:

1. nix run nixpkgs.appimage-run

Expected behavior
This should drop you into an environment with appimage-run installed.

Metadata

• system: "x86_64-linux"
• host os: Linux 5.7.7, NixOS, 20.09pre234194.8d05772134f (Nightingale)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.7
• channels(root): "nixos-20.09pre234194.8d05772134f"
• channels(ivar): "home-manager, nixpkgs-20.09pre234801.1facbd61b17, nixos-20.09pre231796.22a81aa5fc1"
• nixpkgs: /home/ivar/.nix-defexpr/channels/nixpkgs

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute: appimage-run