Fix #2183 porterstemmer causes make json to fail

Drop PorterStemmer package support.
For now, PyStemmer can accelarate stemming process of snowballstemmer.

CHANGES

@@ -21,6 +21,7 @@ Bugs fixed
 * #2071: Fix same footnote in more than two section titles => LaTeX/PDF Bug
 * #2040: Fix UnicodeDecodeError in sphinx-apidoc when author contains non-ascii characters
 * #2193: Fix shutil.SameFileError if source directory and destination directory are same
+* #2183: Fix porterstemmer causes `make json` to fail
 
 
 Release 1.3.3 (released Dec 2, 2015)

sphinx/search/en.py

@@ -12,16 +12,9 @@
 from sphinx.search import SearchLanguage
 
 try:
-    # http://bitbucket.org/methane/porterstemmer/
-    from porterstemmer import Stemmer as CStemmer
-    CSTEMMER = True
-    PYSTEMMER = False
-except ImportError:
-    CSTEMMER = False
-    try:
     from Stemmer import Stemmer as PyStemmer
     PYSTEMMER = True
-    except ImportError:
+except ImportError:
     from sphinx.util.stemmer import PorterStemmer
     PYSTEMMER = False
 
@@ -231,11 +224,7 @@ class SearchEnglish(SearchLanguage):
     stopwords = english_stopwords
 
     def init(self, options):
-        if CSTEMMER:
-            class Stemmer(CStemmer):
-                def stem(self, word):
-                    return self(word.lower())
-        elif PYSTEMMER:
+        if PYSTEMMER:
             class Stemmer(object):
                 def __init__(self):
                     self.stemmer = PyStemmer('porter')