[skip ci] Use PEP 3151 exceptions + custom exception type

Unit tests are not yet adopted.

pycyphal/application/file.py

@@ -9,6 +9,7 @@
 import typing
 import pathlib
 import logging
+import io
 import itertools
 import numpy as np
 import pycyphal
@@ -749,36 +750,52 @@ class FileTimeoutError(pycyphal.application.NetworkTimeoutError):
     """
 
 
+def _raise_if_error(error: Error, filename: str) -> None:
+    if error.value == Error.OK:
+        return
+
+    _logger.error(f"Decoded error value {error.value}")
+
+    exc_types = {
+        Error.NOT_FOUND: FileNotFoundError,
+        Error.ACCESS_DENIED: PermissionError,
+        Error.IS_DIRECTORY: IsADirectoryError,
+        Error.NOT_SUPPORTED: io.UnsupportedOperation,
+    }
+
+    if error.value in exc_types.keys():
+        raise exc_types.get(error.value)(filename)
+
+    raise FileError(error, filename)
+
+
 _perror_uavcan = {
     Error.OK: "OK",
     Error.UNKNOWN_ERROR: "Unknown error",
-    Error.NOT_FOUND: "Not found",  # FileNotFoundError
+    Error.NOT_FOUND: "Not found",
     Error.IO_ERROR: "I/O error",
-    Error.ACCESS_DENIED: "Access denied",  # PermissionError
-    Error.IS_DIRECTORY: "Is a directory",  # IsADirectoryError
+    Error.ACCESS_DENIED: "Access denied",
+    Error.IS_DIRECTORY: "Is a directory",
     Error.INVALID_VALUE: "Invalid value",
     Error.FILE_TOO_LARGE: "File too large",
     Error.OUT_OF_SPACE: "Out of space",
-    Error.NOT_SUPPORTED: "Not supported",  # io.UnsupportedOperation
+    Error.NOT_SUPPORTED: "Not supported",
 }
 
 
-def _raise_if_error(error: Error, filename: str) -> None:
-    if error.value == Error.OK:
-        return
-
-    raise OSError(error.value, _perror_uavcan[error.value], filename)
-    # alternative:
-    # raise FileError(error, filename)
-
-
-class FileError(OSError):
+class FileError(Exception):
     """
-    Exception type specialized for uavcan.file.Error.
+    Exception type specialized for ``uavcan.file.Error``.
     """
 
-    def __init__(self, error: Error, filename: str):
-        super().__init__(error.value, _perror_uavcan[error.value], filename)
+    def __init__(self, error: Error, what: str):
+        error_desc = _perror_uavcan.get(error.value, _perror_uavcan[Error.UNKNOWN_ERROR])
+        super().__init__(f"Error: {error_desc} ({error.value}) {what}")
+        self._error_code = error.value
+
+    @property
+    def error_code(self):
+        return self._error_code
 
 
 _logger = logging.getLogger(__name__)