Methode for http basic auth with username and password added (#80)

* Added methode to allow http basic auth with username and password to BaseDruidClient

* added missing import

* show full error message

pydruid/client.py

@@ -22,13 +22,19 @@
 from six.moves import urllib
 
 from pydruid.query import QueryBuilder
-
+from base64 import b64encode
 
 class BaseDruidClient(object):
     def __init__(self, url, endpoint):
         self.url = url
         self.endpoint = endpoint
         self.query_builder = QueryBuilder()
+        self.username = None
+        self.password = None
+
+    def set_basic_auth_credentials(self, username, password):
+        self.username = username
+        self.password = password
 
     def _prepare_url_headers_and_body(self, query):
         querystr = json.dumps(query.query_dict).encode('utf-8')
@@ -37,6 +43,11 @@ def _prepare_url_headers_and_body(self, query):
         else:
             url = self.url + '/' + self.endpoint
         headers = {'Content-Type': 'application/json'}
+        if (self.username is not None) and (self.password is not None):
+            username_password = \
+                b64encode(bytes('{}:{}'.format(self.username, self.password)))
+            headers['Authorization'] = 'Basic {}'.format(username_password)
+
         return headers, querystr, url
 
     def _post(self, query):
@@ -481,8 +492,6 @@ def _post(self, query):
                     err = json.loads(e.read().decode("utf-8"))
                 except (ValueError, AttributeError, KeyError):
                     pass
-                else:
-                    err = err.get('error', None)
 
             raise IOError('{0} \n Druid Error: {1} \n Query is: {2}'.format(
                     e, err, json.dumps(query.query_dict, indent=4)))