error: look-behind requires fixed-width pattern Spacy - python-2.7

Question

I created a customized Spacy model using https://github.com/explosion/spaCy/blob/master/examples/training/train_ner.py and when I am loading this model. It shows an error - look-behind requires fixed-width pattern. I am confused about how to solve this issue. Please help me. Any help will be appreciated. Thanks in advance.
output_dir = 'NLP_entity/model'
print("Loading from", output_dir)
nlp2 = spacy.load("NLP_entity/model")
test_text = "Remove from account"
#print()
doc2 = nlp1(test_text)
print(test_text)
#print()
if doc2.ents:
for ent in doc2.ents:
print("entity = {}, text = {}".format(ent.label_, ent.text))
else:
print("Entities in None")
Error:
('Loading from', 'NLP_entity/model')
errorTraceback (most recent call last)
<ipython-input-1-94981b2ca322> in <module>()
2 output_dir = 'NLP_entity/model'
3 print("Loading from", output_dir)
----> 4 nlp2 = spacy.load("NLP_entity/model")
5 test_text = "Remove from account".decode("utf-8")
6 #print()
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/spacy/__init__.pyc in load(name, **overrides)
25 if depr_path not in (True, False, None):
26 deprecation_warning(Warnings.W001.format(path=depr_path))
---> 27 return util.load_model(name, **overrides)
28
29
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/spacy/util.pyc in load_model(name, **overrides)
131 return load_model_from_package(name, **overrides)
132 if Path(name).exists(): # path to model data directory
--> 133 return load_model_from_path(Path(name), **overrides)
134 elif hasattr(name, "exists"): # Path or Path-like to model data
135 return load_model_from_path(name, **overrides)
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/spacy/util.pyc in load_model_from_path(model_path, meta, **overrides)
171 component = nlp.create_pipe(name, config=config)
172 nlp.add_pipe(component, name=name)
--> 173 return nlp.from_disk(model_path)
174
175
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/spacy/language.pyc in from_disk(self, path, exclude, disable)
784 # Convert to list here in case exclude is (default) tuple
785 exclude = list(exclude) + ["vocab"]
--> 786 util.from_disk(path, deserializers, exclude)
787 self._path = path
788 return self
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/spacy/util.pyc in from_disk(path, readers, exclude)
609 # Split to support file names like meta.json
610 if key.split(".")[0] not in exclude:
--> 611 reader(path / key)
612 return path
613
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/site-packages/spacy/language.pyc in <lambda>(p)
774 deserializers["meta.json"] = lambda p: self.meta.update(srsly.read_json(p))
775 deserializers["vocab"] = lambda p: self.vocab.from_disk(p) and _fix_pretrained_vectors_name(self)
--> 776 deserializers["tokenizer"] = lambda p: self.tokenizer.from_disk(p, exclude=["vocab"])
777 for name, proc in self.pipeline:
778 if name in exclude:
tokenizer.pyx in spacy.tokenizer.Tokenizer.from_disk()
tokenizer.pyx in spacy.tokenizer.Tokenizer.from_bytes()
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/re.pyc in compile(pattern, flags)
192 def compile(pattern, flags=0):
193 "Compile a regular expression pattern, returning a pattern object."
--> 194 return _compile(pattern, flags)
195
196 def purge():
/home/ubuntu/anaconda3/envs/python2/lib/python2.7/re.pyc in _compile(*key)
249 p = sre_compile.compile(pattern, flags)
250 except error, v:
--> 251 raise error, v # invalid expression
252 if not bypass_cache:
253 if len(_cache) >= _MAXCACHE:
error: look-behind requires fixed-width pattern