Fix TypeError when using F2 without some source

blueyed · blueyed · commit 55b9c7a27aac · 2016-05-31T20:09:45.000+02:00
File "/usr/lib/python3.5/site-packages/bpython/cli.py", line 977, in p_key
        self.statusbar.message(_(e))
      File "/usr/lib/python3.5/site-packages/bpython/cli.py", line 1605, in message
        self.settext(s)
      File "/usr/lib/python3.5/site-packages/bpython/cli.py", line 1655, in settext
        if len(s) &gt;= self.w:
    TypeError: object of type 'SourceNotFound' has no len()

I have used the same code as with `bpython/curtsiesfrontend/repl.py`.
diff --git a/bpython/cli.py b/bpython/cli.py
@@ -974,7 +974,7 @@ def p_key(self, key):
             try:
                 source = self.get_source_of_current_name()
             except repl.SourceNotFound as e:
-                self.statusbar.message(_(e))
+                self.statusbar.message(str(e))
             else:
                 if config.highlight_show_source:
                     source = format(PythonLexer().get_tokens(source),
