let add_history take strings for pyreadline <= 1.5

IPython/utils/rlineimpl.py

@@ -24,6 +24,18 b' except ImportError:'
     except ImportError:    
         have_readline = False
 
+if have_readline and hasattr(_rl, 'rlmain'):
+    # patch add_history to allow for strings in pyreadline <= 1.5:
+    # fix copied from pyreadline 1.6
+    import pyreadline
+    if pyreadline.release.version <= '1.5':
+        def add_history(line):
+            """add a line to the history buffer."""
+            from pyreadline import lineobj
+            if not isinstance(line, lineobj.TextLine):
+                line = lineobj.TextLine(line)
+            return _rl.add_history(line)
+
 if sys.platform == 'win32' and have_readline:
     try:
         _outputfile=_rl.GetOutputFile()