Fix crash due to unpicklable exc_info

Author: rotu

colcon_core/package_identification/python.py

@@ -4,7 +4,6 @@
 
 import multiprocessing
 import os
-import traceback
 from typing import Optional
 
 from colcon_core.dependency_descriptor import DependencyDescriptor
@@ -90,13 +89,13 @@ def get_setup_result(setup_py, *, env: Optional[dict]):
         p.start()
         p.join()
     with conn_recv:
-        result_or_exc_info = conn_recv.recv()
+        result_or_exception_string = conn_recv.recv()
 
-    if isinstance(result_or_exc_info, dict):
-        return result_or_exc_info
+    if isinstance(result_or_exception_string, dict):
+        return result_or_exception_string
     raise RuntimeError(
         'Failure when trying to run setup script {}:\n{}'
-        .format(setup_py, traceback.format_exception(*result_or_exc_info)))
+        .format(setup_py, result_or_exception_string))
 
 
 def _get_setup_result_target(setup_py: str, env: Optional[dict], conn_send):
@@ -108,11 +107,11 @@ def _get_setup_result_target(setup_py: str, env: Optional[dict], conn_send):
 
     :param setup_py: Absolute path to a setup.py script
     :param env: Environment variables to set before running setup.py
-    :param conn_send: Connection to send the result as either a dict or the
-        result of sys.exc_info
+    :param conn_send: Connection to send the result as either a dict or an
+        error string
     """
     import distutils.core
-    import sys
+    import traceback
     try:
         # need to be in setup.py's parent dir to detect any setup.cfg
         os.chdir(os.path.dirname(setup_py))
@@ -140,7 +139,7 @@ def _get_setup_result_target(setup_py: str, env: Optional[dict], conn_send):
                 and not attr.startswith('_')
             )})
     except BaseException:
-        conn_send.send(sys.exc_info())
+        conn_send.send(traceback.format_exc())
         raise