pytest target: add USE_TERMINAL flag

The added flag enables non-buffered console output when using Ninja
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 9a5fc53..eae177e 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -162,9 +162,15 @@
   set(PYBIND11_PYTEST_FOUND TRUE CACHE INTERNAL "")
 endif()
 
+if(CMAKE_VERSION VERSION_LESS 3.2)
+  set(PYBIND11_USES_TERMINAL "")
+else()
+  set(PYBIND11_USES_TERMINAL "USES_TERMINAL")
+endif()
+
 # A single command to compile and run the tests
 add_custom_target(pytest COMMAND ${PYTHON_EXECUTABLE} -m pytest ${PYBIND11_PYTEST_FILES}
-                  DEPENDS pybind11_tests WORKING_DIRECTORY ${testdir})
+                  DEPENDS pybind11_tests WORKING_DIRECTORY ${testdir} ${PYBIND11_USES_TERMINAL})
 
 if(PYBIND11_TEST_OVERRIDE)
   add_custom_command(TARGET pytest POST_BUILD
diff --git a/tests/test_enum.py b/tests/test_enum.py
index 46292f4..6cc4887 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -116,6 +116,7 @@
     assert state2 == -7
     assert int(state ^ state2) == -1
 
+
 def test_enum_to_int():
     from pybind11_tests import Flags, ClassWithUnscopedEnum
     from pybind11_tests import test_enum_to_int, test_enum_to_uint, test_enum_to_long_long