prometheus-xmpp-alerts: Fix broken binary

The binary was broken after the update to 0.5.6 (#205559) due to a
regression in upstream (the module name was changed but not updated in
the appropriate entrypoint). A patch is applied until fixed in upstream.
A very simple test should detect future regressions like this and prevent
breaking the package and associated module.

pkgs/servers/monitoring/prometheus/xmpp-alerts.nix

@@ -2,6 +2,9 @@
 , fetchFromGitHub
 , python3Packages
 , prometheus-alertmanager
+, fetchpatch
+, runCommand
+, prometheus-xmpp-alerts
 }:
 
 python3Packages.buildPythonApplication rec {
@@ -15,6 +18,16 @@ python3Packages.buildPythonApplication rec {
     sha256 = "sha256-PwShGS1rbfZCK5OS6Cnn+mduOpWAD4fC69mcGB5GB1c=";
   };
 
+  patches = [
+    # Required until https://github.com/jelmer/prometheus-xmpp-alerts/pull/33 is merged
+    # and contained in a release
+    (fetchpatch {
+      name = "Fix-outdated-entrypoint-definiton.patch";
+      url = "https://github.com/jelmer/prometheus-xmpp-alerts/commit/c41dd41dbd3c781b874bcf0708f6976e6252b621.patch";
+      hash = "sha256-G7fRLSXbkI5EDgGf4n9xSVs54IPD0ev8rTEFffRvLY0=";
+    })
+  ];
+
   postPatch = ''
     substituteInPlace setup.cfg \
       --replace "bs4" "beautifulsoup4"
@@ -39,6 +52,14 @@ python3Packages.buildPythonApplication rec {
 
   pythonImportsCheck = [ "prometheus_xmpp" ];
 
+  passthru.tests = {
+    binaryWorks = runCommand "${pname}-binary-test" {} ''
+      # Running with --help to avoid it erroring due to a missing config file
+      ${prometheus-xmpp-alerts}/bin/prometheus-xmpp-alerts --help | tee $out
+      grep "usage: prometheus-xmpp-alerts" $out
+    '';
+  };
+
   meta = {
     description = "XMPP Web hook for Prometheus";
     homepage = "https://github.com/jelmer/prometheus-xmpp-alerts";