Make is_valid_poscar less noisy (#422)

* Make `is_valid_poscar` less noisy

* pre-commit auto-fixes

---------

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

Author: Andrew-S-Rosen

src/custodian/vasp/utils.py

@@ -125,20 +125,13 @@ def is_valid_poscar(filename: str, directory: str = "./") -> bool:
     """
     filepath = os.path.join(directory, filename)
 
-    # Check file exists
-    if not os.path.isfile(filepath):
-        logger.warning(f"{filename} does not exist in {directory}")
-        return False
-
-    # Check file is not empty
-    if os.path.getsize(filepath) == 0:
-        logger.warning(f"{filename} is empty")
+    # Check file exists and is not blank
+    if not os.path.isfile(filepath) or os.path.getsize(filepath) == 0:
         return False
 
     # Try to parse as POSCAR
     try:
         Poscar.from_file(filepath)
         return True
-    except Exception as exc:
-        logger.warning(f"{filename} could not be parsed: {exc}")
+    except Exception:
         return False