check file existence in try/catch block instead of using os.path.is_file

anvil-python/anvil/commands/haproxy.py

@@ -15,7 +15,6 @@
 
 import ipaddress
 import logging
-import os.path
 from typing import Any, Callable, List
 
 from rich.console import Console
@@ -48,38 +47,38 @@
 def validate_cert_file(filepath: str) -> None:
     if filepath == "":
         return
-    if not os.path.isfile(filepath):
-        raise ValueError(f"{filepath} does not exist")
     try:
         with open(filepath) as f:
             if "BEGIN CERTIFICATE" not in f.read():
                 raise ValueError("Invalid certificate file")
+    except FileNotFoundError:
+        raise ValueError(f"{filepath} does not exist")
     except PermissionError:
         raise ValueError(f"Permission denied when trying to read {filepath}")
 
 
 def validate_key_file(filepath: str) -> None:
     if filepath == "":
         return
-    if not os.path.isfile(filepath):
-        raise ValueError(f"{filepath} does not exist")
     try:
         with open(filepath) as f:
             if "BEGIN PRIVATE KEY" not in f.read():
                 raise ValueError("Invalid key file")
+    except FileNotFoundError:
+        raise ValueError(f"{filepath} does not exist")
     except PermissionError:
         raise ValueError(f"Permission denied when trying to read {filepath}")
 
 
 def validate_cacert_chain(filepath: str) -> None:
     if filepath == "":
         return
-    if not os.path.isfile(filepath):
-        raise ValueError(f"{filepath} does not exist")
     try:
         # just make sure we can open the file
         with open(filepath):
             pass
+    except FileNotFoundError:
+        raise ValueError(f"{filepath} does not exist")
     except PermissionError:
         raise ValueError(f"Permission denied when trying to read {filepath}")