Revert "Fix formatting and remove unused code"

This reverts commit d7898d586f.

spacy/util.py

@@ -6,12 +6,12 @@ import json
 import re
 import os.path
 import pathlib
+
 import six
 import textwrap
 
 from .attrs import TAG, HEAD, DEP, ENT_IOB, ENT_TYPE
 
-
 try:
     basestring
 except NameError:
@@ -76,6 +76,20 @@ def split_data_name(name):
     return name.split('-', 1) if '-' in name else (name, '')
 
 
+def constraint_match(constraint_string, version):
+    # From http://github.com/spacy-io/sputnik
+    if not constraint_string:
+        return True
+
+    constraints = [c.strip() for c in constraint_string.split(',') if c.strip()]
+
+    for c in constraints:
+        if not re.match(r'[><=][=]?\d+(\.\d+)*', c):
+            raise ValueError('invalid constraint: %s' % c)
+
+    return all(semver.match(version, c) for c in constraints)
+
+
 def read_regex(path):
     path = path if not isinstance(path, basestring) else pathlib.Path(path)
     with path.open() as file_: