device_tests: upgrade get_marker to get_closest_marker

This bumps pytest requirement to 3.6. But we have that everywhere already.
For bonus points, get_closest_marker still exists in 4.1.

requirements-dev.txt

@@ -1,6 +1,6 @@
 -r requirements.txt
 -r requirements-optional.txt
-pytest>=3.2.5
+pytest>=3.6
 flake8
 protobuf
 isort

trezorlib/tests/device_tests/conftest.py

@@ -111,17 +111,17 @@ def pytest_runtest_setup(item):
     * no test should have both skips at the same time
     * allows to 'runxfail' tests specified by 'run_xfail' in pytest.ini
     """
-    if item.get_marker("skip_t1") and item.get_marker("skip_t2"):
+    if item.get_closest_marker("skip_t1") and item.get_closest_marker("skip_t2"):
         pytest.fail("Don't skip tests for both trezors!")
 
-    if item.get_marker("skip_t2") and TREZOR_VERSION == 2:
+    if item.get_closest_marker("skip_t2") and TREZOR_VERSION == 2:
         pytest.skip("Test excluded on Trezor T")
-    if item.get_marker("skip_t1") and TREZOR_VERSION == 1:
+    if item.get_closest_marker("skip_t1") and TREZOR_VERSION == 1:
         pytest.skip("Test excluded on Trezor 1")
 
-    xfail = item.get_marker("xfail")
+    xfail = item.get_closest_marker("xfail")
     runxfail_markers = item.config.getini("run_xfail")
-    run_xfail = any(item.get_marker(marker) for marker in runxfail_markers)
+    run_xfail = any(item.get_closest_marker(marker) for marker in runxfail_markers)
     if xfail and run_xfail:
         # Deep hack: pytest's private _evalxfail helper determines whether the test should xfail or not.
         # The helper caches its result even before this hook runs.