Improve SafeRe code readability

function isSafePattern was never used as boolean function, its only
useful behaviour being raising exception on bad regexp, so it's renamed
and reused accordingly

src/util/SafeRe.py

@@ -7,7 +7,8 @@ class UnsafePatternError(Exception):
 cached_patterns = {}
 
 
-def isSafePattern(pattern):
+def guard(pattern):
+    '''Checks if pattern is safe and raises exception if it isn't'''
     if len(pattern) > 255:
         raise UnsafePatternError("Pattern too long: %s characters in %s" % (len(pattern), pattern))
 
@@ -20,14 +21,13 @@ def isSafePattern(pattern):
     if len(repetitions1) + len(repetitions2) >= 10:
         raise UnsafePatternError("More than 10 repetitions in %s" % pattern)
 
-    return True
-
 
 def match(pattern, *args, **kwargs):
+    '''Guard for safety, compile, cache and match regexp'''
     cached_pattern = cached_patterns.get(pattern)
     if cached_pattern:
         return cached_pattern.match(*args, **kwargs)
     else:
-        if isSafePattern(pattern):
-            cached_patterns[pattern] = re.compile(pattern)
-            return cached_patterns[pattern].match(*args, **kwargs)
+        guard(pattern)
+        cached_patterns[pattern] = re.compile(pattern)
+        return cached_patterns[pattern].match(*args, **kwargs)