simplified solution

auth.py

@@ -39,19 +39,11 @@ def add_user(username, pwdb):
     return pwdb
 
 def read_pwdb(pwdb_path):
-    # try to read from the database
-    # if anything happens, report the error!
     if not pwdb_path.exists():
-        initialize_pwdb(pwdb_path)
-    try:
+        pwdb = {}
+    else:
         with open(pwdb_path, 'rt') as pwdb_file:
             pwdb = json.load(pwdb_file)
-    except json.decoder.JSONDecodeError as exc:
-        # this happens when the json data is invalid
-        raise Exception(f'Invalid database {pwdb_path}: {exc}')
-    except Exception as exc:
-        # this is a catch-all condition
-        raise Exception(f'Unkown error reading {pwdb_path}: {exc}')
     return pwdb
 
 def write_pwdb(pwdb, pwdb_path):
@@ -72,9 +64,6 @@ def get_salt():
     salt_chars = random.choices(CHARS, k=SALT_LENGTH)
     return ''.join(salt_chars)
 
-def initialize_pwdb(pwdb_path):
-    write_pwdb({}, pwdb_path)
-
 def main(pwdb_path):
     # load the password database from file
     pwdb = read_pwdb(pwdb_path)
@@ -87,17 +76,11 @@ def main(pwdb_path):
 
     # ask for credentials
     username, password = get_credentials()
-
-    if username not in pwdb:
-        print('Wrong username!')
-        return
-
-    # try to authenticate
-    if authenticate(username, password, pwdb):
-        print('Successfully authenticated!')
+    if username not in pwdb or not authenticate(username, password, pwdb):
+        print('Wrong username or password!')
     else:
-        # report wrong password
-        print('Wrong password!')
+        print('Successfully authenticated!')
+
     return
 
 if __name__ == '__main__':