Revert patching of breakpointhook as it appears to do nothing

changelog/4028.trivial.rst

@@ -0,0 +1 @@
+Revert patching of ``sys.breakpointhook`` since it appears to do nothing.

src/_pytest/debugging.py

@@ -2,18 +2,10 @@
 from __future__ import absolute_import, division, print_function
 import pdb
 import sys
-import os
 from doctest import UnexpectedException
 
 from _pytest.config import hookimpl
 
-try:
-    from builtins import breakpoint  # noqa
-
-    SUPPORTS_BREAKPOINT_BUILTIN = True
-except ImportError:
-    SUPPORTS_BREAKPOINT_BUILTIN = False
-
 
 def pytest_addoption(parser):
     group = parser.getgroup("general")
@@ -51,20 +43,12 @@ def pytest_configure(config):
     if config.getvalue("usepdb"):
         config.pluginmanager.register(PdbInvoke(), "pdbinvoke")
 
-    # Use custom Pdb class set_trace instead of default Pdb on breakpoint() call
-    if SUPPORTS_BREAKPOINT_BUILTIN:
-        _environ_pythonbreakpoint = os.environ.get("PYTHONBREAKPOINT", "")
-        if _environ_pythonbreakpoint == "":
-            sys.breakpointhook = pytestPDB.set_trace
-
     old = (pdb.set_trace, pytestPDB._pluginmanager)
 
     def fin():
         pdb.set_trace, pytestPDB._pluginmanager = old
         pytestPDB._config = None
         pytestPDB._pdb_cls = pdb.Pdb
-        if SUPPORTS_BREAKPOINT_BUILTIN:
-            sys.breakpointhook = sys.__breakpointhook__
 
     pdb.set_trace = pytestPDB.set_trace
     pytestPDB._pluginmanager = config.pluginmanager

testing/test_pdb.py

@@ -4,9 +4,15 @@
 import os
 
 import _pytest._code
-from _pytest.debugging import SUPPORTS_BREAKPOINT_BUILTIN
 import pytest
 
+try:
+    breakpoint
+except NameError:
+    SUPPORTS_BREAKPOINT_BUILTIN = False
+else:
+    SUPPORTS_BREAKPOINT_BUILTIN = True
+
 
 _ENVIRON_PYTHONBREAKPOINT = os.environ.get("PYTHONBREAKPOINT", "")