Handle ValueError in signal registration on Python 3.14+

Catch ValueError raised when calling signal.signal from a non-main thread or non-main interpreter context (e.g. sub-interpreters on Python 3.14+). Falls back to synchronous execution without a timeout.

Signed-off-by: Eshaan Agrawal <agrawaleshaan12@gmail.com>

Author: eshaanag

src/scancode/interrupt.py

@@ -93,11 +93,23 @@ def handler(signum, frame):
         except TimeoutError:
             return TIMEOUT_MSG % locals(), NO_VALUE
 
+        except ValueError as ve:
+            if 'signal only works in main thread' in str(ve):
+                # Fallback to running without timeout if we are not in the main thread of the main interpreter
+                try:
+                    return NO_ERROR, func(*(args or ()), **(kwargs or {}))
+                except Exception:
+                    return ERROR_MSG + traceback_format_exc(), NO_VALUE
+            return ERROR_MSG + traceback_format_exc(), NO_VALUE
+
         except Exception:
             return ERROR_MSG + traceback_format_exc(), NO_VALUE
 
         finally:
-            setitimer(ITIMER_REAL, 0)
+            try:
+                setitimer(ITIMER_REAL, 0)
+            except ValueError:
+                pass
 
 elif on_windows:
     """