title: '_sre.SRE_Pattern' object is not iterable in Python 3.4
body: <p>When I use Brill Tagger, I get this error.</p>
  
  <pre><code>TypeError: '_sre.SRE_Pattern' object is not iterable
  WARNING:root:2016-04-05 00:05:37.503718 is when this event was logged.
  ERROR:root:'_sre.SRE_Pattern' object is not iterable
  Traceback (most recent call last):
    File "D:\Dropbox\VCL\MyWrapper.py", line 137, in run_alg
      CLC_POS.tag_file(input_utf8, path_out + '.pos', file_encoding, CLC_POS.load_tagger('pos_tbl_86943.model'), '')
    File "D:\Dropbox\VCL\CLC_POS.py", line 277, in tag_file
      token_tag = tagger.tag(word_list)
    File "C:\Python34\lib\site-packages\nltk\tag\brill.py", line 264, in tag
      tagged_tokens = self._initial_tagger.tag(tokens)
    File "C:\Python34\lib\site-packages\nltk\tag\sequential.py", line 61, in tag
      tags.append(self.tag_one(tokens, i, tags))
    File "C:\Python34\lib\site-packages\nltk\tag\sequential.py", line 81, in tag_one
      tag = tagger.choose_tag(tokens, index, history)
    File "C:\Python34\lib\site-packages\nltk\tag\sequential.py", line 546, in choose_tag
      for regexp, tag in self._regexs:
  TypeError: '_sre.SRE_Pattern' object is not iterable
  </code></pre>
  
  <p>In sequential.py, I get error when it comes to <strong>for</strong> loop.</p>
  
  <pre><code>def choose_tag(self, tokens, index, history):
      for regexp, tag in self._regexs:
          if re.match(regexp, tokens[index]):
              return tag
      return None
  </code></pre>
  
  <p>I run this same code a month ago and there was no error.
  <em>sequential.py</em> belongs to nltk files, does that means I should mess with it?</p>
  
  <p>What have I done wrong? Please provide a fix if possible.</p>