Use internal atomicwrites implementation and drop dependency

Fix #10114

changelog/10114.trivial.rst

@@ -0,0 +1 @@
+Dropped the dependency to `atomicwrites <https://github.com/untitaker/python-atomicwrites>`__ library.

setup.cfg

@@ -46,7 +46,6 @@ install_requires =
     packaging
     pluggy>=0.12,<2.0
     py>=1.8.2
-    atomicwrites>=1.0;sys_platform=="win32"
     colorama;sys_platform=="win32"
     importlib-metadata>=0.12;python_version<"3.8"
     tomli>=1.0.0;python_version<"3.11"

src/_pytest/assertion/rewrite.py

@@ -303,7 +303,7 @@ def _write_pyc_fp(
 
 
 if sys.platform == "win32":
-    from atomicwrites import atomic_write
+    from _pytest.atomic_writes import atomic_write
 
     def _write_pyc(
         state: "AssertionState",