Remove indexing from ubuntu corpus trainer

This seems to be failing on some systems.

chatterbot/trainers.py

@@ -5,7 +5,6 @@
 from multiprocessing import Pool, Manager
 from dateutil import parser as date_parser
 from chatterbot.conversation import Statement
-from chatterbot.tagging import PosLemmaTagger
 from chatterbot import utils
 
 
@@ -176,7 +175,7 @@ def train(self, *corpus_paths):
             self.chatbot.storage.create_many(statements_to_create)
 
 
-def read_file(files, queue, preprocessors, tagger):
+def read_file(files, queue, preprocessors):
 
     statements_from_file = []
 
@@ -200,11 +199,9 @@ def read_file(files, queue, preprocessors, tagger):
                     for preprocessor in preprocessors:
                         statement = preprocessor(statement)
 
-                    statement.search_text = tagger.get_bigram_pair_string(statement.text)
                     statement.search_in_response_to = previous_statement_search_text
 
                     previous_statement_text = statement.text
-                    previous_statement_search_text = statement.search_text
 
                     statements_from_file.append(statement)
 
@@ -325,8 +322,6 @@ def track_progress(members):
     def train(self):
         import glob
 
-        tagger = PosLemmaTagger(language=self.chatbot.storage.tagger.language)
-
         # Download and extract the Ubuntu dialog corpus if needed
         corpus_download_path = self.download(self.data_download_url)
 
@@ -355,8 +350,7 @@ def chunks(items, items_per_chunk):
             (
                 file_names,
                 queue,
-                self.chatbot.preprocessors,
-                tagger,
+                self.chatbot.preprocessors
             ) for file_names in file_groups
         )