Update app.py

app.py

@@ -37,13 +37,14 @@ except Exception:
 # ---------------------------------------------------------------------------
 
 def run_capture(cmd):
-    """Run a command and return stdout, raise RuntimeError with stderr on failure."""
+    """Run a command and return stdout; raise RuntimeError with readable stderr on failure."""
     result = subprocess.run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True)
     if result.returncode != 0:
-        err_tail = result.stderr[-1000:] if result.stderr else ""
+        stderr_text = result.stderr or ""
+        # Keep only tail to avoid massive logs
+        tail = stderr_text[-2000:]
         raise RuntimeError("Command failed: " + " ".join(cmd) + "
-" + err_tail)
-{err_tail}")
+" + tail)
     return result.stdout