local_timezone: gracefully handle retrieval errors on Darwin

In some sandbox environments, the program may not have
permission to access /etc/localtime or it may not exist.

Catch any exceptions accessing and parsing its value and return UTC by
default to avoid crashing the program.

src/pendulum/tz/local_timezone.py

@@ -146,9 +146,16 @@ def _get_windows_timezone() -> Timezone:
 
 
 def _get_darwin_timezone() -> Timezone:
-    # link will be something like /usr/share/zoneinfo/America/Los_Angeles.
-    link = os.readlink("/etc/localtime")
-    tzname = link[link.rfind("zoneinfo/") + 9 :]
+    try:
+        # link will be something like /usr/share/zoneinfo/America/Los_Angeles.
+        link = os.readlink("/etc/localtime")
+        tzname = link[link.rfind("zoneinfo/") + 9 :]
+    except Exception:
+        warnings.warn(
+            "Unable to find any timezone configuration, defaulting to UTC.", stacklevel=1
+        )
+
+        return UTC
 
     return Timezone(tzname)