i1673 add tests for python3 exceptions

IPython/core/tests/test_ultratb.py

@@ -9,6 +9,7 b' from IPython.testing import tools as tt'
 from IPython.testing.decorators import onlyif_unicode_paths
 from IPython.utils.syspathcontext import prepended_to_syspath
 from IPython.utils.tempdir import TemporaryDirectory
+from IPython.utils.py3compat import PY3
 
 ip = get_ipython()
 
@@ -147,3 +148,37 b' class SyntaxErrorTest(unittest.TestCase):'
         except ValueError:
             with tt.AssertPrints('QWERTY'):
                 ip.showsyntaxerror()
+
+
+class Python3ChainedExceptionsTest(unittest.TestCase):
+    DIRECT_CAUSE_ERROR_CODE = """
+try:
+    x = 1 + 2
+    print(not_defined_here)
+except Exception as e:
+    x += 55
+    x - 1
+    y = {}
+    raise KeyError('uh') from e
+    """
+
+    EXCEPTION_DURING_HANDLING_CODE = """
+try:
+    x = 1 + 2
+    print(not_defined_here)
+except Exception as e:
+    x += 55
+    x - 1
+    y = {}
+    raise KeyError('uh')
+    """
+
+    def test_direct_cause_error(self):
+        if PY3:
+            with tt.AssertPrints(["KeyError", "NameError", "direct cause"]):
+                ip.run_cell(self.DIRECT_CAUSE_ERROR_CODE)
+
+    def test_exception_during_handling_error(self):
+        if PY3:
+            with tt.AssertPrints(["KeyError", "NameError", "During handling"]):
+                ip.run_cell(self.EXCEPTION_DURING_HANDLING_CODE)