Print exception instead of "KeyboardInterrupt"

Whenever a KeyboardInterrupt exception occurs in the shell, we should
print the actual exception instead of the string "KeyboardInterrupt".
This is needed to support exceptions inherited from KeyboardInterrupt.

IPython/core/debugger.py

@@ -277,7 +277,7 b' class Pdb(OldPdb):'
             try:
                 OldPdb.interaction(self, frame, traceback)
             except KeyboardInterrupt:
-                self.shell.write("\nKeyboardInterrupt\n")
+                self.shell.write('\n' + self.shell.get_exception_only())
                 break
             else:
                 break

IPython/core/interactiveshell.py

@@ -22,6 +22,7 b' import re'
 import runpy
 import sys
 import tempfile
+import traceback
 import types
 import subprocess
 from io import open as io_open
@@ -1786,6 +1787,15 b' class InteractiveShell(SingletonConfigurable):'
         """
         self.write_err("UsageError: %s" % exc)
     
+    def get_exception_only(self, exc_tuple=None):
+        """
+        Return as a string (ending with a newline) the exception that
+        just occurred, without any traceback.
+        """
+        etype, value, tb = self._get_exc_info(exc_tuple)
+        msg = traceback.format_exception_only(etype, value)
+        return ''.join(msg)
+
     def showtraceback(self, exc_tuple=None, filename=None, tb_offset=None,
                       exception_only=False):
         """Display the exception that just occurred.
@@ -1838,7 +1848,7 b' class InteractiveShell(SingletonConfigurable):'
                 self._showtraceback(etype, value, stb)
 
         except KeyboardInterrupt:
-            self.write_err("\nKeyboardInterrupt\n")
+            self.write_err('\n' + self.get_exception_only())
 
     def _showtraceback(self, etype, evalue, stb):
         """Actually show a traceback.
@@ -2355,7 +2365,7 b' class InteractiveShell(SingletonConfigurable):'
                 try:
                     ec = os.system(cmd)
                 except KeyboardInterrupt:
-                    self.write_err("\nKeyboardInterrupt\n")
+                    self.write_err('\n' + self.get_exception_only())
                     ec = -2
         else:
             cmd = py3compat.unicode_to_str(cmd)
@@ -2374,7 +2384,7 b' class InteractiveShell(SingletonConfigurable):'
                 ec = subprocess.call(cmd, shell=True, executable=executable)
             except KeyboardInterrupt:
                 # intercept control-C; a long traceback is not useful here
-                self.write_err("\nKeyboardInterrupt\n")
+                self.write_err('\n' + self.get_exception_only())
                 ec = 130
             if ec > 128:
                 ec = -(ec - 128)

IPython/core/tests/test_interactiveshell.py

@@ -482,6 +482,21 b' class InteractiveShellTestCase(unittest.TestCase):'
         mod = ip.new_main_mod(u'%s.py' % name, name)
         self.assertEqual(mod.__name__, name)
 
+    def test_get_exception_only(self):
+        try:
+            raise KeyboardInterrupt
+        except KeyboardInterrupt:
+            msg = ip.get_exception_only()
+        self.assertEqual(msg, 'KeyboardInterrupt\n')
+
+        class DerivedInterrupt(KeyboardInterrupt):
+            pass
+        try:
+            raise DerivedInterrupt("foo")
+        except KeyboardInterrupt:
+            msg = ip.get_exception_only()
+        self.assertEqual(msg, 'DerivedInterrupt: foo\n')
+
 class TestSafeExecfileNonAsciiPath(unittest.TestCase):
 
     @onlyif_unicode_paths

IPython/terminal/console/interactiveshell.py

@@ -529,7 +529,7 b' class ZMQTerminalInteractiveShell(TerminalInteractiveShell):'
             except KeyboardInterrupt:
                 #double-guard against keyboardinterrupts during kbdint handling
                 try:
-                    self.write('\nKeyboardInterrupt\n')
+                    self.write('\n' + self.get_exception_only())
                     source_raw = self.input_splitter.raw_reset()
                     hlen_b4_cell = self._replace_rlhist_multiline(source_raw, hlen_b4_cell)
                     more = False

IPython/terminal/interactiveshell.py

@@ -468,7 +468,7 b' class TerminalInteractiveShell(InteractiveShell):'
             except KeyboardInterrupt:
                 #double-guard against keyboardinterrupts during kbdint handling
                 try:
-                    self.write('\nKeyboardInterrupt\n')
+                    self.write('\n' + self.get_exception_only())
                     source_raw = self.input_splitter.raw_reset()
                     hlen_b4_cell = \
                         self._replace_rlhist_multiline(source_raw, hlen_b4_cell)