Catch errors in querying readline which occur with pyreadline.

IPython/core/interactiveshell.py

@@ -144,23 +144,29 b' class ReadlineNoRecord(object):'
         
     def __enter__(self):
         if self._nested_level == 0:
-            self.orig_length = self.current_length()
-            self.readline_tail = self.get_readline_tail()
+            try:
+                self.orig_length = self.current_length()
+                self.readline_tail = self.get_readline_tail()
+            except (AttributeError, IndexError):   # Can fail with pyreadline
+                self.orig_length, self.readline_tail = 999999, []
         self._nested_level += 1
         
     def __exit__(self, type, value, traceback):
         self._nested_level -= 1
         if self._nested_level == 0:
             # Try clipping the end if it's got longer
-            e = self.current_length() - self.orig_length
-            if e > 0:
-                for _ in range(e):
-                    self.shell.readline.remove_history_item(self.orig_length)
-            
-            # If it still doesn't match, just reload readline history.
-            if self.current_length() != self.orig_length \
-                or self.get_readline_tail() != self.readline_tail:
-                self.shell.refill_readline_hist()
+            try:
+                e = self.current_length() - self.orig_length
+                if e > 0:
+                    for _ in range(e):
+                        self.shell.readline.remove_history_item(self.orig_length)
+                
+                # If it still doesn't match, just reload readline history.
+                if self.current_length() != self.orig_length \
+                    or self.get_readline_tail() != self.readline_tail:
+                    self.shell.refill_readline_hist()
+            except (AttributeError, IndexError):
+                pass
         # Returning False will cause exceptions to propagate
         return False