New ASSETS and trackers GMC cleanup (#4425)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/utils/checks.py

@@ -20,7 +20,7 @@ import requests
 import torch
 from matplotlib import font_manager
 
-from ultralytics.utils import (AUTOINSTALL, LOGGER, ONLINE, ROOT, USER_CONFIG_DIR, ThreadingLocked, TryExcept,
+from ultralytics.utils import (ASSETS, AUTOINSTALL, LOGGER, ONLINE, ROOT, USER_CONFIG_DIR, ThreadingLocked, TryExcept,
                                clean_url, colorstr, downloads, emojis, is_colab, is_docker, is_jupyter, is_kaggle,
                                is_online, is_pip_package, url2file)
 
@@ -460,8 +460,7 @@ def check_amp(model):
         del m
         return a.shape == b.shape and torch.allclose(a, b.float(), atol=0.5)  # close to 0.5 absolute tolerance
 
-    f = ROOT / 'assets/bus.jpg'  # image to check
-    im = f if f.exists() else 'https://ultralytics.com/images/bus.jpg' if ONLINE else np.ones((640, 640, 3))
+    im = ASSETS / 'bus.jpg'  # image to check
     prefix = colorstr('AMP: ')
     LOGGER.info(f'{prefix}running Automatic Mixed Precision (AMP) checks with YOLOv8n...')
     warning_msg = "Setting 'amp=True'. If you experience zero-mAP or NaN losses you can disable AMP with amp=False."
@@ -484,11 +483,9 @@ def check_amp(model):
 
 def git_describe(path=ROOT):  # path must be a directory
     """Return human-readable git description, i.e. v5.0-5-g3e25f1e https://git-scm.com/docs/git-describe."""
-    try:
-        assert (Path(path) / '.git').is_dir()
+    with contextlib.suppress(Exception):
         return subprocess.check_output(f'git -C {path} describe --tags --long --always', shell=True).decode()[:-1]
-    except AssertionError:
-        return ''
+    return ''
 
 
 def print_args(args: Optional[dict] = None, show_file=True, show_func=False):