lib.ProcFilterGpg: Add module

Add a ProcFilter implementation for decrypting GPG blobs. It needs an
ExecContext passed to __init__() in order to run /usr/bin/gpg.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/ProcFilterGpg.py

@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import annotations
+from typing import TYPE_CHECKING
+
+from .ProcFilter import ProcFilter
+from .base import Result
+
+if TYPE_CHECKING:
+    from .ExecContext import ExecContext
+
+class ProcFilterGpg(ProcFilter):
+
+    def __init__(self, ec: ExecContext) -> None:
+        self.__ec = ec
+
+    async def _run(self, data: bytes) -> Result:
+        return await self.__ec.run([
+                "gpg",
+                '--batch',
+                '--yes',
+                '--quiet',
+                '--no-tty',
+                '--decrypt',
+            ],
+            cmd_input = data,
+            throw = True
+        )