--- a/cubicweb/migration.py	Wed May 22 17:08:09 2019 +0200
+++ b/cubicweb/migration.py	Wed May 22 17:10:06 2019 +0200
@@ -200,7 +200,7 @@
             return meth(*args, **kwargs)
 
     def confirm(self, question, # pylint: disable=E0202
-                shell=True, abort=True, retry=False, pdb=False, default='y'):
+                shell=True, abort=True, retry=False, pdb=False, default='y', traceback=None):
         """ask for confirmation and return true on positive answer
 
         if `retry` is true the r[etry] answer may return 2
@@ -226,11 +226,14 @@
             raise SystemExit(1)
         if answer == 'shell':
             self.interactive_shell()
-            return self.confirm(question, shell, abort, retry, pdb, default)
+            return self.confirm(question, shell, abort, retry, pdb, default, traceback)
         if answer == 'pdb':
             pdb = utils.get_pdb()
-            pdb.set_trace()
-            return self.confirm(question, shell, abort, retry, pdb, default)
+            if traceback:
+                pdb.post_mortem(traceback)
+            else:
+                pdb.set_trace()
+            return self.confirm(question, shell, abort, retry, pdb, default, traceback)
         return True
 
     def interactive_shell(self):

--- a/cubicweb/server/migractions.py	Wed May 22 17:08:09 2019 +0200
+++ b/cubicweb/server/migractions.py	Wed May 22 17:10:06 2019 +0200
@@ -262,9 +262,10 @@
         source = repo.system_source
         try:
             source.restore(osp.join(tmpdir, source.uri), self.confirm, drop, format)
-        except Exception as exc:
+        except Exception:
+            _, exc, traceback_ = sys.exc_info()
             print('-> error trying to restore %s [%s]' % (source.uri, exc))
-            if not self.confirm('Continue anyway?', default='n'):
+            if not self.confirm('Continue anyway?', default='n', pdb=True, traceback=traceback_):
                 raise SystemExit(1)
         finally:
             shutil.rmtree(tmpdir)
@@ -1454,8 +1455,9 @@
             try:
                 cu = self.cnx.system_sql(sql, args)
             except Exception:
-                ex = sys.exc_info()[1]
-                if self.confirm('Error: %s\nabort?' % ex, pdb=True):
+                _, ex, traceback_ = sys.exc_info()
+                if self.confirm('Error: %s\nabort?' % ex,
+                                pdb=True, traceback=traceback_):
                     raise
                 return
             try:
@@ -1479,8 +1481,10 @@
             if not ask_confirm or self.confirm('Execute rql: %s ?' % msg):
                 try:
                     res = execute(rql, kwargs, build_descr=build_descr)
-                except Exception as ex:
-                    if self.confirm('Error: %s\nabort?' % ex, pdb=True):
+                except Exception:
+                    _, ex, traceback_ = sys.exc_info()
+                    if self.confirm('Error: %s\nabort?' % ex,
+                                    pdb=True, traceback=traceback_):
                         raise
         return res
 
@@ -1568,8 +1572,10 @@
                 raise StopIteration
         try:
             return self._h._cw.execute(rql, kwargs)
-        except Exception as ex:
-            if self._h.confirm('Error: %s\nabort?' % ex):
+        except Exception:
+            _, ex, traceback_ = sys.exc_info()
+            if self._h.confirm('Error: %s\nabort?' % ex,
+                               pdb=True, traceback=traceback_):
                 raise
             else:
                 raise StopIteration

--- a/cubicweb/test/unittest_migration.py	Wed May 22 17:08:09 2019 +0200
+++ b/cubicweb/test/unittest_migration.py	Wed May 22 17:10:06 2019 +0200
@@ -18,14 +18,18 @@
 """cubicweb.migration unit tests"""
 
 from os.path import dirname, join
+from unittest.mock import patch
+
 from logilab.common.testlib import TestCase, unittest_main
 
-from cubicweb import devtools
+from cubicweb import devtools, utils
+from logilab.common.shellutils import ASK
 from cubicweb.cwconfig import CubicWebConfiguration
 from cubicweb.migration import (
     filter_scripts,
     split_constraint,
     version_strictly_lower,
+    MigrationHelper,
 )
 
 
@@ -128,5 +132,54 @@
     assert split_constraint("<= 42.1.0") == ("<=", "42.1.0")
 
 
+class WontColideWithOtherExceptionsException(Exception):
+    pass
+
+
+class MigrationHelperTC(TestCase):
+    @patch.object(utils, 'get_pdb')
+    @patch.object(ASK, 'ask', return_value="pdb")
+    def test_confirm_no_traceback(self, ask, get_pdb):
+        post_mortem = get_pdb.return_value.post_mortem
+        set_trace = get_pdb.return_value.set_trace
+
+        # we need to break after post_mortem is called otherwise we get
+        # infinite recursion
+        set_trace.side_effect = WontColideWithOtherExceptionsException
+
+        mh = MigrationHelper(config=None)
+
+        with self.assertRaises(WontColideWithOtherExceptionsException):
+            mh.confirm("some question")
+
+        get_pdb.assert_called_once()
+        set_trace.assert_called_once()
+        post_mortem.assert_not_called()
+
+    @patch.object(utils, 'get_pdb')
+    @patch.object(ASK, 'ask', return_value="pdb")
+    def test_confirm_got_traceback(self, ask, get_pdb):
+        post_mortem = get_pdb.return_value.post_mortem
+        set_trace = get_pdb.return_value.set_trace
+
+        # we need to break after post_mortem is called otherwise we get
+        # infinite recursion
+        post_mortem.side_effect = WontColideWithOtherExceptionsException
+
+        mh = MigrationHelper(config=None)
+
+        fake_traceback = object()
+
+        with self.assertRaises(WontColideWithOtherExceptionsException):
+            mh.confirm("some question", traceback=fake_traceback)
+
+        get_pdb.assert_called_once()
+        set_trace.assert_not_called()
+        post_mortem.assert_called_once()
+
+        # we want post_mortem to actually receive the traceback
+        self.assertEqual(post_mortem.call_args, ((fake_traceback,),))
+
+
 if __name__ == '__main__':
     unittest_main()