Fix hak check for matrix-seshat (backport #33030) (#33063)

apps/desktop/hak/matrix-seshat/check.ts

@@ -14,10 +14,7 @@ import type { Tool } from "../../scripts/hak/hakEnv.ts";
 import type { DependencyInfo } from "../../scripts/hak/dep.ts";
 
 export default async function (hakEnv: HakEnv, moduleInfo: DependencyInfo): Promise<void> {
-    const tools: Tool[] = [
+    const tools: Tool[] = [["rustc", "--version"]];
-        ["rustc", "--version"],
-        ["python", "--version"], // node-gyp uses python for reasons beyond comprehension
-    ];
     if (hakEnv.isWin()) {
         tools.push(["perl", "--version"]); // for openssl configure
         tools.push(["nasm", "-v"]); // for openssl building
@@ -28,6 +25,14 @@ export default async function (hakEnv: HakEnv, moduleInfo: DependencyInfo): Prom
     }
     await hakEnv.checkTools(tools);
 
+    try {
+        // node-gyp uses python for reasons beyond comprehension
+        // Try python3 first, to get a more sensible error if python is not found in the fallback
+        await hakEnv.checkTools([["python3", "--version"]]);
+    } catch {
+        await hakEnv.checkTools([["python", "--version"]]);
+    }
+
     // Ensure Rust target exists (nb. we avoid depending on rustup)
     await new Promise((resolve, reject) => {
         const rustc = childProcess.execFile(

apps/desktop/scripts/hak/hakEnv.ts

@@ -103,6 +103,9 @@ export default class HakEnv {
                 shell: this.isWin(),
                 ...options,
             });
+            proc.on("error", (err) => {
+                reject(err);
+            });
             proc.on("exit", (code) => {
                 if (code) {
                     reject(code);