Add support for pytest fixtures from local pytest plugins.

test/completion/conftest.py

@@ -27,3 +27,9 @@ def capsysbinary(capsysbinary):
     #? ['close']
     capsysbinary.clos
     return capsysbinary
+
+
+# used when fixtures are defined in multiple files
+pytest_plugins = [
+    "completion.fixture_module",
+]

test/completion/fixture_module.py

@@ -0,0 +1,6 @@
+# Exists only for completion/pytest.py
+import pytest
+
+@pytest.fixture
+def my_module_fixture():
+    return 1.0

test/completion/pytest.py

@@ -96,6 +96,9 @@ def test_x(my_con
 #? 18 ['my_conftest_fixture']
 def test_x(my_conftest_fixture):
     return
+#? ['my_module_fixture']
+def test_x(my_modu
+    return
 
 #? []
 def lala(my_con