Remove dependency on the extras library

requirements.txt

@@ -9,4 +9,3 @@ testtools>=2.2.0 # MIT
 PyYAML>=3.10.0 # MIT
 voluptuous>=0.8.9 # BSD License
 tomlkit>=0.11.6 # MIT
-extras>=1.0.0

stestr/repository/memory.py

@@ -12,8 +12,7 @@
 
 """In memory storage of test results."""
 
-from extras import try_import
-
+from collections import OrderedDict
 from io import BytesIO
 from operator import methodcaller
 
@@ -22,8 +21,6 @@
 
 from stestr.repository import abstract as repository
 
-OrderedDict = try_import("collections.OrderedDict", dict)
-
 
 class RepositoryFactory(repository.AbstractRepositoryFactory):
     """A factory that can initialise and open memory repositories.

stestr/subunit_runner/program.py

@@ -18,8 +18,6 @@
 import sys
 import unittest
 
-import extras
-
 
 def filter_by_ids(suite_or_case, test_ids):
     """Remove tests from suite_or_case where their id is not in test_ids.
@@ -59,10 +57,10 @@ def filter_by_ids(suite_or_case, test_ids):
     than guessing how to reconstruct a new suite.
     """
     # Compatible objects
-    if extras.safe_hasattr(suite_or_case, "filter_by_ids"):
+    if hasattr(suite_or_case, "filter_by_ids"):
         return suite_or_case.filter_by_ids(test_ids)
     # TestCase objects.
-    if extras.safe_hasattr(suite_or_case, "id"):
+    if hasattr(suite_or_case, "id"):
         if suite_or_case.id() in test_ids:
             return suite_or_case
         else:
@@ -197,7 +195,7 @@ def __init__(
             self.runTests()
         else:
             runner = self._get_runner()
-            if extras.safe_hasattr(runner, "list"):
+            if hasattr(runner, "list"):
                 try:
                     runner.list(self.test, loader=self.testLoader)
                 except TypeError:

stestr/testlist.py

@@ -14,10 +14,15 @@
 
 import io
 
-from extras import try_import
-
-bytestream_to_streamresult = try_import("subunit.ByteStreamToStreamResult")
-stream_result = try_import("testtools.testresult.doubles.StreamResult")
+try:
+    from subunit import ByteStreamToStreamResult as bytestream_to_streamresult
+except ImportError:
+    bytestream_to_streamresult = None
+
+try:
+    from testtools.testresult.doubles import StreamResult as stream_result
+except ImportError:
+    stream_result = None
 
 
 def write_list(stream, test_ids):