Update lhaindex.py

validphys2/src/validphys/lhaindex.py

@@ -133,6 +133,10 @@ def parse_info(name):
 def get_lha_datapath():
     """Return an existing datapath from LHAPDF, starting from the end.
     If no path is found to exist, recover the old behaviour and returns the last path.
+
+    The check for existence intends to solve problems where a previously filled `LHAPATH`
+    or `LHAPDF_DATA_PATH` environment variable is pointing to a non-existent path or shared
+    systems where LHAPDF might be compiled with hard-coded paths not available to all users.
     """
     for lhapath in lhapdf.paths()[::-1]:
         if Path(lhapath).exists():