utcfromtimestamp was deprecated and nobody told me,

not even the deprecationwarning that got silently generated burning
20~30% of all CPU-time without actually displaying it anywhere, nice

python 3.12.0 is now only 5% slower than 3.11.6

also fixes some other, less-performance-fatal deprecations

.vscode/launch.py

@@ -41,7 +41,7 @@ if sfx:
     argv = [sys.executable, sfx] + argv
     sp.check_call(argv)
 elif re.search(" -j ?[0-9]", " ".join(argv)):
-    argv = [sys.executable, "-m", "copyparty"] + argv
+    argv = [sys.executable, "-Wa", "-m", "copyparty"] + argv
     sp.check_call(argv)
 else:
     sys.path.insert(0, os.getcwd())