3.x fix import fallback

packages/yarnpkg-cli/sources/main.ts

@@ -10,30 +10,26 @@ import {pluginCommands}
 function runBinary(path: PortablePath) {
   const physicalPath = npath.fromPortablePath(path);
 
+  if (!physicalPath) {
+    throw Object.assign(
+      new Error(`runBinary ${path} ENOENT`),
+      {code: `ENOENT`, errno: -2},
+    );
+  }
+
   process.on(`SIGINT`, () => {
     // We don't want SIGINT to kill our process; we want it to kill the
     // innermost process, whose end will cause our own to exit.
   });
 
-  if (physicalPath) {
-    execFileSync(process.execPath, [physicalPath, ...process.argv.slice(2)], {
-      stdio: `inherit`,
-      env: {
-        ...process.env,
-        YARN_IGNORE_PATH: `1`,
-        YARN_IGNORE_CWD: `1`,
-      },
-    });
-  } else {
-    execFileSync(physicalPath, process.argv.slice(2), {
-      stdio: `inherit`,
-      env: {
-        ...process.env,
-        YARN_IGNORE_PATH: `1`,
-        YARN_IGNORE_CWD: `1`,
-      },
-    });
-  }
+  execFileSync(process.execPath, [physicalPath, ...process.argv.slice(2)], {
+    stdio: `inherit`,
+    env: {
+      ...process.env,
+      YARN_IGNORE_PATH: `1`,
+      YARN_IGNORE_CWD: `1`,
+    },
+  });
 }
 
 export async function main({binaryVersion, pluginConfiguration}: {binaryVersion: string, pluginConfiguration: PluginConfiguration}) {
@@ -99,14 +95,16 @@ export async function main({binaryVersion, pluginConfiguration}: {binaryVersion:
       await exec(cli);
       return;
     } else if (yarnPath !== null && !ignorePath) {
-      if (!xfs.existsSync(yarnPath)) {
-        process.stdout.write(cli.error(new Error(`The "yarn-path" option has been set (in ${configuration.sources.get(`yarnPath`)}), but the specified location doesn't exist (${yarnPath}).`)));
-        process.exitCode = 1;
-      } else {
-        try {
-          runBinary(yarnPath);
-        } catch (error) {
-          process.exitCode = error.code || 1;
+      try {
+        runBinary(yarnPath);
+      } catch (error) {
+        if (error.code === `ENOENT`)
+          process.stdout.write(cli.error(new Error(`The "yarn-path" option has been set (in ${configuration.sources.get(`yarnPath`)}), but the specified location doesn't exist (${yarnPath}).`)));
+
+        if (typeof error.code === `number`) {
+          process.exitCode = error.code;
+        } else {
+          process.exitCode = 1;
         }
       }
     } else {