Remove use of unicode_literals as it is an anti-pattern

from __future__ unicode_literals leads to developer confusion as
developers no longer can tell whether a bare literal string is a byte
string or a unicode string.  Explicit marking as u"" or b"" is the way
to solve the same problem in the Ansbile codebase.

docs/docsite/rst/dev_guide/testing/sanity/no-unicode-literals.rst

@@ -0,0 +1,16 @@
+Sanity Tests » no-unicode_literals
+==================================
+
+The use of :code:`from __future__ import unicode_literals` has been deemed an anti-pattern.  The
+problems with it are:
+
+* It makes it so one can't jump into the middle of a file and know whether a bare literal string is
+  a byte string or text string.  The programmer has to first check the top of the file to see if the
+  import is there.
+* It removes the ability to define native strings (a string which should be a byte string on python2
+  and a text string on python3) via a string literal.
+* It makes for more context switching.  A programmer could be reading one file which has
+  `unicode_literals` and know that bare string literals are text strings but then switch to another
+  file (perhaps tracing program execution into a third party library) and have to switch their
+  understanding of what bare string literals are.
+

lib/ansible/plugins/lookup/mongodb.py

@@ -88,7 +88,6 @@ EXAMPLES:
 '''
 
 from __future__ import (absolute_import, division, print_function)
-from __future__ import unicode_literals
 from ansible.module_utils.six import string_types, integer_types
 import datetime
 
@@ -120,7 +119,7 @@ class LookupModule(LookupBase):
             return sort_parameter
 
         if not isinstance(sort_parameter, list):
-            raise AnsibleError("Error. Sort parameters must be a list, not [ {} ]".format(sort_parameter))
+            raise AnsibleError(u"Error. Sort parameters must be a list, not [ {} ]".format(sort_parameter))
 
         for item in sort_parameter:
             self._convert_sort_string_to_constant(item)
@@ -130,9 +129,9 @@ class LookupModule(LookupBase):
     def _convert_sort_string_to_constant(self, item):
         original_sort_order = item[1]
         sort_order = original_sort_order.upper()
-        if sort_order == "ASCENDING":
+        if sort_order == u"ASCENDING":
             item[1] = ASCENDING
-        elif sort_order == "DESCENDING":
+        elif sort_order == u"DESCENDING":
             item[1] = DESCENDING
         # else the user knows what s/he is doing and we won't predict. PyMongo will return an error if necessary
 
@@ -159,13 +158,13 @@ class LookupModule(LookupBase):
             return (result - datetime.datetime(1970, 1, 1)). total_seconds()
         else:
             # failsafe
-            return "{}".format(result)
+            return u"{}".format(result)
 
     def run(self, terms, variables, **kwargs):
 
         ret = []
         for term in terms:
-            '''
+            u'''
             Makes a MongoDB query and returns the output as a valid list of json.
             Timestamps are converted to epoch integers/longs.
 
@@ -206,20 +205,20 @@ class LookupModule(LookupBase):
 -------------------------------------------------------------------------------
             '''
 
-            connection_string = term.get('connection_string', "mongodb://localhost")
-            database = term["database"]
-            collection = term['collection']
-            extra_connection_parameters = term.get('extra_connection_parameters', {})
+            connection_string = term.get(u'connection_string', u"mongodb://localhost")
+            database = term[u"database"]
+            collection = term[u'collection']
+            extra_connection_parameters = term.get(u'extra_connection_parameters', {})
 
-            if "extra_connection_parameters" in term:
-                del term["extra_connection_parameters"]
-            if "connection_string" in term:
-                del term["connection_string"]
-            del term["database"]
-            del term["collection"]
+            if u"extra_connection_parameters" in term:
+                del term[u"extra_connection_parameters"]
+            if u"connection_string" in term:
+                del term[u"connection_string"]
+            del term[u"database"]
+            del term[u"collection"]
 
-            if "sort" in term:
-                term["sort"] = self._fix_sort_parameter(term["sort"])
+            if u"sort" in term:
+                term[u"sort"] = self._fix_sort_parameter(term[u"sort"])
 
             # all other parameters are sent to mongo, so we are future and past proof
 
@@ -232,6 +231,6 @@ class LookupModule(LookupBase):
                     ret.append(result)
 
             except ConnectionFailure as e:
-                raise AnsibleError('unable to connect to database: %s' % str(e))
+                raise AnsibleError(u'unable to connect to database: %s' % str(e))
 
         return ret

test/sanity/code-smell/no-unicode-literals.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+
+UNICODE_LITERALS_USERS=$(grep -r unicode_literals . \
+    --exclude-dir .git \
+    --exclude-dir .tox \
+    --exclude no-unicode-literals.sh \
+    --exclude no-unicode-literals.rst |
+    grep -v ./test/results \
+    )
+
+if [ "${UNICODE_LITERALS_USERS}" ]; then
+    echo "${UNICODE_LITERALS_USERS}"
+    exit 1
+fi
+
+exit 0