Adding explicit python 3.5.3 test to nox, travis.

Copied 3.5.4 definition of typing.Deque

Author: anselor

.travis.yml

@@ -2,6 +2,9 @@ language: python
 
 matrix:
     include:
+        - os: linux
+          python: 3.5.3
+          env: NOXSESSION=tests-3.5.3
         - os: linux
           python: 3.5
           env: NOXSESSION=tests-3.5

CHANGELOG.md

@@ -1,3 +1,11 @@
+## 1.3.3 (TBD)
+* Bug Fixes
+    * Added explicit testing against python 3.5.3 for Debian 9 support.
+    * Added fallback definition of typing.Deque (taken from 3.5.4)
+* Other 
+    * Added missing doc-string for new cmd2.Cmd __init__ parameters 
+      introduced by CommandSet enhancement
+
 ## 1.3.2 (August 10, 2020)
 * Bug Fixes
     * Fixed `prog` value of subcommands added with `as_subcommand_to()` decorator.

cmd2/table_creator.py

@@ -22,8 +22,17 @@
 except ImportError:  # pragma: no cover
     import typing
 
+    # The following copied from the implementation of Deque in Python 3.5.4
     # noinspection PyProtectedMember, PyUnresolvedReferences
-    Deque = typing._alias(deque, typing.T)
+    class Deque(deque, typing.MutableSequence[typing.T]):
+        __slots__ = ()
+        __extra__ = deque
+
+        def __new__(cls, *args, **kwds):
+            if typing._geqv(cls, Deque):
+                raise TypeError('Type Deque cannot be instantiated; use deque() instead')
+            return typing._generic_new(deque, cls, *args, **kwds)
+
 
 # Constants
 EMPTY = ''

noxfile.py

@@ -14,7 +14,7 @@ def docs(session):
                 '-d', '{}/doctrees'.format(tmpdir), '.', '{}/html'.format(tmpdir))
 
 
-@nox.session(python=['3.5', '3.6', '3.7', '3.8', '3.9'])
+@nox.session(python=['3.5.3', '3.5', '3.6', '3.7', '3.8', '3.9'])
 @nox.parametrize('plugin', [None,
                             'ext_test',
                             'template',