diff --git a/src/_pytest/fixtures.py b/src/_pytest/fixtures.py
index 34ecf2e21..44802e000 100644
--- a/src/_pytest/fixtures.py
+++ b/src/_pytest/fixtures.py
@@ -36,6 +36,7 @@ if False:  # TYPE_CHECKING
     from typing import Type
 
     from _pytest import nodes
+    from _pytest.main import Session
 
 
 @attr.s(frozen=True)
@@ -44,7 +45,7 @@ class PseudoFixtureDef:
     scope = attr.ib()
 
 
-def pytest_sessionstart(session):
+def pytest_sessionstart(session: "Session"):
     import _pytest.python
     import _pytest.nodes
 
@@ -510,13 +511,11 @@ class FixtureRequest:
             values.append(fixturedef)
             current = current._parent_request
 
-    def _compute_fixture_value(self, fixturedef):
+    def _compute_fixture_value(self, fixturedef: "FixtureDef") -> None:
         """
         Creates a SubRequest based on "self" and calls the execute method of the given fixturedef object. This will
         force the FixtureDef object to throw away any previous results and compute a new fixture value, which
         will be stored into the FixtureDef object itself.
-
-        :param FixtureDef fixturedef:
         """
         # prepare a subrequest object before calling fixture function
         # (latter managed by fixturedef)
@@ -544,9 +543,8 @@ class FixtureRequest:
             if has_params:
                 frame = inspect.stack()[3]
                 frameinfo = inspect.getframeinfo(frame[0])
-                source_path = frameinfo.filename
+                source_path = py.path.local(frameinfo.filename)
                 source_lineno = frameinfo.lineno
-                source_path = py.path.local(source_path)
                 if source_path.relto(funcitem.config.rootdir):
                     source_path = source_path.relto(funcitem.config.rootdir)
                 msg = (
diff --git a/src/_pytest/main.py b/src/_pytest/main.py
index e46f54d9c..53bfbeb5a 100644
--- a/src/_pytest/main.py
+++ b/src/_pytest/main.py
@@ -15,6 +15,7 @@ from _pytest import nodes
 from _pytest.config import directory_arg
 from _pytest.config import hookimpl
 from _pytest.config import UsageError
+from _pytest.fixtures import FixtureManager
 from _pytest.outcomes import exit
 from _pytest.runner import collect_one_node
 from _pytest.runner import SetupState
@@ -372,6 +373,7 @@ class Session(nodes.FSCollector):
     Interrupted = Interrupted
     Failed = Failed
     _setupstate = None  # type: SetupState
+    _fixturemanager = None  # type: FixtureManager
 
     def __init__(self, config):
         nodes.FSCollector.__init__(