fix: add graceful fallback when ColorBrewer palette loading fails offline

Wrap the urllib.request.urlopen() call in _load_colorbrewer() with try/except
to handle network failures gracefully. When offline or the remote gist is
unreachable, PyMOL will now print a warning and continue startup normally
instead of crashing with an unhandled exception.

Changes:
- Add try/except around the HTTP request in _load_colorbrewer()
- Add timeout=5 to prevent long hangs on slow/unreachable networks
- Print a descriptive warning message on failure and return early

Author: Cloud

configs/.pymolrc.py

@@ -79,7 +79,11 @@ def should_check() -> bool:
 def _load_colorbrewer():
     """Load ColorBrewer palettes into PyMOL."""
     url = "https://gist.githubusercontent.com/frankrowe/9007567/raw/colorbrewer.js"
-    js_text = urllib.request.urlopen(url).read().decode("utf-8")
+    try:
+        js_text = urllib.request.urlopen(url, timeout=5).read().decode("utf-8")
+    except Exception as exc:
+        print(f"Warning: unable to load ColorBrewer palettes ({exc}). Skipping.")
+        return
 
     # Extract the JavaScript object containing the ColorBrewer palettes
     obj_text = re.search(r"var\s+colorbrewer\s*=\s*(\{.*\});", js_text, flags=re.DOTALL).group(1)