[Bug #1526834] Fix crash in pdb when you do 'b f(';

the function name was placed into a regex pattern and the unbalanced paren
caused re.compile() to report an error

Lib/pdb.py

@@ -23,7 +23,7 @@ __all__ = ["run", "pm", "Pdb", "runeval", "runctx", "runcall", "set_trace",
            "post_mortem", "help"]
 
 def find_function(funcname, filename):
-    cre = re.compile(r'def\s+%s\s*[(]' % funcname)
+    cre = re.compile(r'def\s+%s\s*[(]' % re.escape(funcname))
     try:
         fp = open(filename)
     except IOError: