plugin: Use pytest 5.4.0 new Function API

pytest_asyncio/plugin.py

@@ -36,13 +36,13 @@ def pytest_configure(config):
 def pytest_pycollect_makeitem(collector, name, obj):
     """A pytest hook to collect asyncio coroutines."""
     if collector.funcnamefilter(name) and _is_coroutine(obj):
-        item = pytest.Function(name, parent=collector)
+        item = pytest.Function.from_parent(collector, name=name)
 
         # Due to how pytest test collection works, module-level pytestmarks
         # are applied after the collection step. Since this is the collection
         # step, we look ourselves.
         transfer_markers(obj, item.cls, item.module)
-        item = pytest.Function(name, parent=collector)  # To reload keywords.
+        item = pytest.Function.from_parent(collector, name=name)  # To reload keywords.
 
         if 'asyncio' in item.keywords:
             return list(collector._genfunctions(name, obj))

setup.py

@@ -40,7 +40,7 @@ def find_version():
         "Framework :: Pytest",
     ],
     python_requires=">= 3.5",
-    install_requires=["pytest >= 3.6.0, < 5.4.0"],
+    install_requires=["pytest >= 5.4.0"],
     extras_require={
         ':python_version == "3.5"': "async_generator >= 1.3",
         "testing": [