Minor read pref updates

Add read prefs to aggregate method
Pop all extra read pref kwargs

Author: rozza

pymongo/collection.py

@@ -592,10 +592,10 @@ def find(self, *args, **kwargs):
 
         .. note:: The `max_scan` parameter requires server
            version **>= 1.5.1**
-           
+
         .. versionadded:: 2.2.1+
            The `tag_sets` and `secondary_acceptable_latency_ms` parameters.
-           
+
         .. versionadded:: 1.11+
            The `await_data`, `partial`, and `manipulate` parameters.
 
@@ -928,10 +928,13 @@ def aggregate(self, pipeline):
 
         return self.__database.command("aggregate", self.__name,
                                         pipeline=pipeline,
+                                        read_preference=self.read_preference,
+                                        tag_sets=self.tag_sets,
+                                        secondary_acceptable_latency_ms=(
+                                         self.secondary_acceptable_latency_ms),
                                         slave_okay=self.slave_okay,
                                         _use_master=use_master)
 
-
     # TODO key and condition ought to be optional, but deprecation
     # could be painful as argument order would have to change.
     def group(self, key, condition, initial, reduce, finalize=None):

pymongo/database.py

@@ -368,16 +368,16 @@ def command(self, command, value=1,
             '_uuid_subtype': uuid_subtype
         }
 
-        if not must_use_master:
-            extra_opts['read_preference'] = kwargs.pop(
-                'read_preference',
-                self.read_preference)
-            extra_opts['tag_sets'] = kwargs.pop(
-                'tag_sets',
-                self.tag_sets)
-            extra_opts['secondary_acceptable_latency_ms'] = kwargs.pop(
-                'secondary_acceptable_latency_ms',
-                self.secondary_acceptable_latency_ms)
+
+        extra_opts['read_preference'] = kwargs.pop(
+            'read_preference',
+            self.read_preference)
+        extra_opts['tag_sets'] = kwargs.pop(
+            'tag_sets',
+            self.tag_sets)
+        extra_opts['secondary_acceptable_latency_ms'] = kwargs.pop(
+            'secondary_acceptable_latency_ms',
+            self.secondary_acceptable_latency_ms)
 
         fields = kwargs.get('fields')
         if fields is not None and not isinstance(fields, dict):