util/ctx: extract suppress_oserror()

Extract the `suppress_oserror()` function from the ObjectManager and
make it available as utility for other code as well.

This also adds a bunch of tests that verify it works as expected.

osbuild/util/ctx.py

@@ -0,0 +1,35 @@
+"""ContextManager Utilities
+
+This module implements helpers around python context-managers, with-statements,
+and RAII. It is meant as a supplement to `contextlib` from the python standard
+library.
+"""
+
+import contextlib
+
+
+__all__ = [
+    "suppress_oserror",
+]
+
+
+@contextlib.contextmanager
+def suppress_oserror(*errnos):
+    """Suppress OSError Exceptions
+
+    This is an extension to `contextlib.suppress()` from the python standard
+    library. It catches any `OSError` exceptions and suppresses them. However,
+    it only catches the exceptions that match the specified error numbers.
+
+    Parameters
+    ----------
+    errnos
+        A list of error numbers to match on. If none are specified, this
+        function has no effect.
+    """
+
+    try:
+        yield
+    except OSError as e:
+        if e.errno not in errnos:
+            raise e