refactored deprecated pymongo methods in tests

- remove/count/add_user/insert
- added pymongo_support

mongoengine/pymongo_support.py

@@ -0,0 +1,33 @@
+"""
+Helper functions, constants, and types to aid with PyMongo v2.7 - v3.x support.
+"""
+import pymongo
+
+_PYMONGO_37 = (3, 7)
+
+PYMONGO_VERSION = tuple(pymongo.version_tuple[:2])
+
+IS_PYMONGO_3 = PYMONGO_VERSION[0] >= 3
+IS_PYMONGO_GTE_37 = PYMONGO_VERSION >= _PYMONGO_37
+
+
+def count_documents(collection, filter):
+    """Pymongo>3.7 deprecates count in favour of count_documents"""
+    if IS_PYMONGO_GTE_37:
+        return collection.count_documents(filter)
+    else:
+        count = collection.find(filter).count()
+    return count
+
+
+def list_collection_names(db, include_system_collections=False):
+    """Pymongo>3.7 deprecates collection_names in favour of list_collection_names"""
+    if IS_PYMONGO_GTE_37:
+        collections = db.list_collection_names()
+    else:
+        collections = db.collection_names()
+
+    if not include_system_collections:
+        collections = [c for c in collections if not c.startswith('system.')]
+
+    return collections