Simplify exceptions returned by PythonSession.run

Don't include the first stack entry or the filename (which is <string>).

1 files changed, 10 insertions, 2 deletions

diff --git a/server/python_session.py b/server/python_session.py
index 33fe7cc..62fcbf8 100644
--- a/server/python_session.py
+++ b/server/python_session.py
@@ -172,9 +172,17 @@ def _run_exec(conn, code, expr=None, stdin=''):
         if expr:
             result = eval(expr, env)
     except Exception as ex:
-        # Exception is not JSON serializable, so return traceback as string.
+        # Exception is not JSON serializable, so return traceback as string
+        # (without the first entry, which is this function).
         import traceback
-        exc = traceback.format_exc()
+        e_type, e_value, e_tb = sys.exc_info()
+        stack = traceback.extract_tb(e_tb)
+        exc = ''.join(
+                ['Traceback (most recent call last):\n'] +
+                ['  line {}, in {}\n'.format(lineno, name) + (line+'\n' if line else '')
+                    for filename, lineno, name, line in stack[1:]] +
+                traceback.format_exception_only(e_type, e_value)
+            ).rstrip()
     finally:
         out = sys.stdout.getvalue()
         err = sys.stderr.getvalue()