Fix matplotlib backend computation (#1811)

* Fix matplotlib backend computation and problem found with just my code fix

* Remove extra logging

Author: rchiodo

CONTRIBUTING.md

@@ -201,7 +201,7 @@ If you have an existing test failing, you can investigate it by running the test
 - Clone the repo a second time
 - Change the code in `tests_python/debugger_unittest.py` so that the test prints out logs on success too (by default it only logs the output on a failure)
 - Run the failing test in the second clone
-- Run the failing test in your original clone
+- Run the failing test in your original clone (with the --capture=tee-sys so that it outputs the log)
 - Diff the results by finding the log file name in the output and diffing those two files
 - Add more logging around where the differences first appear
 - Repeat running and diffing

src/debugpy/_vendored/pydevd/_pydevd_sys_monitoring/_pydevd_sys_monitoring.py

@@ -624,10 +624,10 @@ def _get_func_code_info(code_obj, frame_or_depth) -> FuncCodeInfo:
             frame = frame_or_depth
         assert frame.f_code is code_obj
 
-    func_code_info.filtered_out_force_checked = py_db.apply_files_filter(frame, func_code_info.abs_path_filename, py_db.get_use_libraries_filter())
+    func_code_info.filtered_out_force_checked = py_db.apply_files_filter(frame, func_code_info.abs_path_filename, True)
 
     if py_db.is_files_filter_enabled:
-        func_code_info.always_filtered_out = func_code_info.filtered_out_force_checked
+        func_code_info.always_filtered_out = py_db.apply_files_filter(frame, func_code_info.abs_path_filename, False)
         if func_code_info.always_filtered_out:
             _code_to_func_code_info_cache[code_obj] = func_code_info
             return func_code_info
@@ -1163,7 +1163,7 @@ def _return_event(code, instruction, retval):
             or (
                 info.pydev_step_cmd == CMD_STEP_INTO_MY_CODE
                 and frame.f_back is not None
-                and not py_db.apply_files_filter(frame.f_back, frame.f_back.f_code.co_filename, py_db.get_use_libraries_filter())
+                and not py_db.apply_files_filter(frame.f_back, frame.f_back.f_code.co_filename, True)
             )
         ):
             _show_return_values(frame, retval)