python310Packages.perfplot: fix darwin build

pkgs/development/python-modules/perfplot/default.nix

@@ -1,4 +1,5 @@
 { lib
+, stdenv
 , buildPythonPackage
 , fetchFromGitHub
 , flit-core
@@ -35,6 +36,10 @@ buildPythonPackage rec {
     rich
   ];
 
+  # This variable is needed to suppress the "Trace/BPT trap: 5" error in Darwin's checkPhase.
+  # Not sure of the details, but we can avoid it by changing the matplotlib backend during testing.
+  env.MPLBACKEND = lib.optionalString stdenv.isDarwin "Agg";
+
   nativeCheckInputs = [
     pytestCheckHook
   ];