remove references to '2to3' in doc, travis, etc

.landscape.yml

@@ -5,17 +5,12 @@ pylint:
 
     options:
         additional-builtins:
-            # add xrange and long as valid built-ins. In Python 3, xrange is
+            # add long as valid built-ins.
-            # translated into range and long is translated into int via 2to3 (see
-            # "use_2to3" in setup.py). This should be removed when we drop Python
-            # 2 support (which probably won't happen any time soon).
-            - xrange
             - long
 
 pyflakes:
     disable:
-        # undefined variables are already covered by pylint (and exclude
+        # undefined variables are already covered by pylint (and exclude long)
-        # xrange & long)
         - F821
 
 ignore-paths:

.travis.yml

@@ -73,7 +73,7 @@ install:
 before_script:
   - mkdir ${PWD}/mongodb-linux-x86_64-${MONGODB}/data
   - ${PWD}/mongodb-linux-x86_64-${MONGODB}/bin/mongod --dbpath ${PWD}/mongodb-linux-x86_64-${MONGODB}/data --logpath ${PWD}/mongodb-linux-x86_64-${MONGODB}/mongodb.log --fork
-  - if [[ $TRAVIS_PYTHON_VERSION == '2.7' ]]; then flake8 .; else echo "flake8 only runs on py27"; fi   # Run flake8 for Python 2.7 only
+  - if [[ $TRAVIS_PYTHON_VERSION == '3.7' ]]; then flake8 .; else echo "flake8 only runs on py37"; fi         # Run flake8 for Python 3.7 only
   - if [[ $TRAVIS_PYTHON_VERSION == '3.7' ]]; then black --check .; else echo "black only runs on py37"; fi   # Run black for Python 3.7 only
   - mongo --eval 'db.version();'    # Make sure mongo is awake
 
@@ -84,7 +84,7 @@ script:
 # 0% coverage. That's caused by 'use_2to3', which builds the py3-compatible
 # code in a separate dir and runs tests on that.
 after_success:
-- if [[ $TRAVIS_PYTHON_VERSION == '2.7' ]]; then coveralls --verbose; else echo "coveralls only sent for py27"; fi
+- coveralls --verbose
 
 notifications:
   irc: irc.freenode.org#mongoengine

CONTRIBUTING.rst

@@ -22,11 +22,19 @@ Supported Interpreters
 
 MongoEngine supports CPython 2.7 and newer. Language
 features not supported by all interpreters can not be used.
-The codebase is written in python 2 so you must be using python 2
+The codebase is written in a compatible manner for python 2 & 3 so it
-when developing new features. Compatibility of the library with Python 3
+is important that this is taken into account when it comes to discrepencies
-relies on the 2to3 package that gets executed as part of the installation
+between the 2 versions (check this https://python-future.org/compatible_idioms.html).
-build. You should ensure that your code is properly converted by
+Travis runs run the tests against the different versions as a safety net.
-`2to3 <http://docs.python.org/library/2to3.html>`_.
+
+Python 2/3 compatibility
+----------------------
+
+The codebase is written in a compatible manner for python 2 & 3 so it
+is important that this is taken into account when it comes to discrepencies
+between the 2 versions (check this https://python-future.org/compatible_idioms.html).
+Travis runs run the tests against the different versions as a safety net.
+
 
 Style Guide
 -----------

benchmarks/test_inserts.py

@@ -3,13 +3,17 @@ import timeit
 
 def main():
     setup = """
+from builtins import range
+
 from pymongo import MongoClient
+
 connection = MongoClient()
 connection.drop_database('mongoengine_benchmark_test')
 """
 
     stmt = """
 from pymongo import MongoClient
+
 connection = MongoClient()
 
 db = connection.mongoengine_benchmark_test
@@ -55,7 +59,10 @@ myNoddys = noddy.find()
     print("{}s".format(t.timeit(1)))
 
     setup = """
+from builtins import range
+
 from pymongo import MongoClient
+
 connection = MongoClient()
 connection.drop_database('mongoengine_benchmark_test')
 connection.close()

mongoengine/document.py

@@ -71,7 +71,6 @@ class EmbeddedDocument(six.with_metaclass(DocumentMetaclass, BaseDocument)):
 
     __slots__ = ("_instance",)
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = DocumentMetaclass
 
@@ -156,7 +155,6 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
     in the :attr:`meta` dictionary.
     """
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = TopLevelDocumentMetaclass
 
@@ -1045,7 +1043,6 @@ class DynamicDocument(six.with_metaclass(TopLevelDocumentMetaclass, Document)):
         There is one caveat on Dynamic Documents: undeclared fields cannot start with `_`
     """
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = TopLevelDocumentMetaclass
 
@@ -1069,7 +1066,6 @@ class DynamicEmbeddedDocument(six.with_metaclass(DocumentMetaclass, EmbeddedDocu
     information about dynamic documents.
     """
 
-    # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = DocumentMetaclass