very small py3 compat changes

src/rez/cli/_main.py

@@ -4,6 +4,7 @@
 from __future__ import print_function
 
 import sys
+import importlib
 from argparse import _StoreTrueAction, SUPPRESS
 from rez.cli._util import subcommands, LazyArgumentParser, _env_var_true
 from rez.utils.logging_ import print_error
@@ -46,7 +47,7 @@ def __call__(self, parser_name, parser):
 
     def get_module(self):
         if self.module_name not in sys.modules:
-            __import__(self.module_name, globals(), locals(), [], -1)
+            importlib.import_module(self.module_name)
         return sys.modules[self.module_name]
 
 

src/rez/rex.py

@@ -5,7 +5,6 @@
 import sys
 import pipes
 import re
-import UserDict
 import inspect
 import traceback
 from string import Formatter
@@ -932,7 +931,7 @@ def get_value(self, key, args, kwds):
 # Environment Classes
 #===============================================================================
 
-class EnvironmentDict(UserDict.DictMixin):
+class EnvironmentDict(dict):
     """
     Provides a mapping interface to `EnvironmentVariable` instances,
     which provide an object-oriented interface for recording environment

src/rez/utils/scope.py

@@ -1,11 +1,10 @@
 from __future__ import print_function
 
 from rez.utils.formatting import StringFormatMixin, StringFormatType
-import UserDict
 import sys
 
 
-class RecursiveAttribute(UserDict.UserDict, StringFormatMixin):
+class RecursiveAttribute(dict, StringFormatMixin):
     """An object that can have new attributes added recursively::
 
         >>> a = RecursiveAttribute()