If the JSON doesn't load, it's likely because the user has another server running on the same port. Improve the error message here so can figure out what's going on more easily.

Author: speedplane

browsermobproxy/client.py

@@ -29,7 +29,12 @@ def __init__(self, url, params=None, options=None):
             self.port = options['existing_proxy_port_to_use']
         else:
             resp = requests.post('%s/proxy' % self.host + urlparams)
-            jcontent = json.loads(resp.content.decode('utf-8'))
+            content = resp.content.decode('utf-8')
+            try:
+                jcontent = json.loads(content)
+            except Exception as e:
+                raise Exception("Could not read Browsermob-Proxy json\n"
+                    "Another server running on this port?\n%s..."%content[:512])
             self.port = jcontent['port']
         url_parts = self.host.split(":")
         self.proxy = url_parts[1][2:] + ":" + str(self.port)