Use importlib to take place of imp module

The imp module is deprecated[1] since version 3.4, use importlib to
instead

[1]: https://docs.python.org/3/library/imp.html

Change-Id: Ifb44be3b0a0c35dd99d0230e9c371dfcb97f6fdd

troveclient/shell.py

@@ -21,7 +21,7 @@ Command-line interface to the OpenStack Trove API.
 import argparse
 import getpass
 import glob
-import imp
+import importlib
 import itertools
 import logging
 import os
@@ -299,6 +299,14 @@ class OpenStackTroveShell(object):
 
                 yield name, module
 
+    def _load_module(self, name, path):
+        module_spec = importlib.spec_from_file_location(
+            name, path
+        )
+        module = importlib.module_from_spec(module_spec)
+        module_spec.loader.exec_module(module)
+        return module
+
     def _discover_via_contrib_path(self, version):
         module_path = os.path.dirname(os.path.abspath(__file__))
         version_str = "v%s" % version.replace('.', '_')
@@ -312,7 +320,7 @@ class OpenStackTroveShell(object):
             if name == "__init__":
                 continue
 
-            module = imp.load_source(name, ext_path)
+            module = self._load_module(name, ext_path)
             yield name, module
 
     def _discover_via_entry_points(self):

troveclient/tests/test_discover.py

@@ -13,8 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import imp
 import inspect
+import types
 from unittest import mock
 
 import pkg_resources
@@ -31,7 +31,7 @@ class DiscoverTest(testtools.TestCase):
             if group == 'troveclient.extension':
                 fake_ep = mock.Mock()
                 fake_ep.name = 'foo'
-                fake_ep.module = imp.new_module('foo')
+                fake_ep.module = types.ModuleType('foo')
                 fake_ep.load.return_value = fake_ep.module
                 return [fake_ep]
 
@@ -48,13 +48,13 @@ class DiscoverTest(testtools.TestCase):
     def test_discover_extensions(self):
 
         def mock_discover_via_python_path(self):
-            yield 'foo', imp.new_module('foo')
+            yield 'foo', types.ModuleType('foo')
 
         def mock_discover_via_contrib_path(self, version):
-            yield 'bar', imp.new_module('bar')
+            yield 'bar', types.ModuleType('bar')
 
         def mock_discover_via_entry_points(self):
-            yield 'baz', imp.new_module('baz')
+            yield 'baz', types.ModuleType('baz')
 
         @mock.patch.object(troveclient.shell.OpenStackTroveShell,
                            '_discover_via_python_path',