Update corenlp.py

Author: alvations

pycorenlp/corenlp.py

@@ -12,10 +12,12 @@ def annotate(self, text, properties=None):
             properties = {}
 
         # Checks that the Stanford CoreNLP server is started.
-        assert requests.get(nlp.server_url).ok, \
-        str('Check whether you have started the CoreNLP server, e.g. \n'
-        '$ cd stanford-corenlp-full-2015-12-09/ \n'
-        '$ java -mx4g -cp "*" edu.stanford.nlp.pipeline.StanfordCoreNLPServer')
+        try:
+            requests.get(self.server_url).ok == True
+        except requests.exceptions.ConnectionError:
+            raise Exception('Check whether you have started the CoreNLP server e.g.\n'
+            '$ cd stanford-corenlp-full-2015-12-09/ \n'
+            '$ java -mx4g -cp "*" edu.stanford.nlp.pipeline.StanfordCoreNLPServer')
 
         r = requests.get(
             self.server_url, params={