Add user and group wrappers

New classes for user and group names provide a convenient way to access
the uid and primary gid of a user / gid of a group. The classes also
provide chown() and chgrp() methods to simplify common operations.

The wrappers are subclasses of builtin str type and behave like ordinary
strings with additional features. The pwd and grp structs are retrieved
once and then cached.

Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

ipatests/test_ipaplatform/test_constants.py

@@ -0,0 +1,53 @@
+#
+# Copyright (C) 2020  FreeIPA Contributors see COPYING for license
+#
+import pytest
+
+from ipaplatform.base.constants import User, Group
+
+
+def test_user_root():
+    user = User("root")
+    assert user == "root"
+    assert str(user) == "root"
+    assert repr(user) == '<User "root">'
+    assert user.uid == 0
+    assert user.pgid == 0
+    assert user.entity.pw_uid == 0
+
+
+def test_user_invalid():
+    invalid = User("invalid")
+    with pytest.raises(ValueError) as e:
+        assert invalid.uid
+    assert str(e.value) == "user 'invalid' not found"
+
+
+def test_group():
+    group = Group("root")
+    assert group == "root"
+    assert str(group) == "root"
+    assert repr(group) == '<Group "root">'
+    assert group.gid == 0
+    assert group.entity.gr_gid == 0
+
+
+def test_group_invalid():
+    invalid = Group("invalid")
+    with pytest.raises(ValueError) as e:
+        assert invalid.gid
+    assert str(e.value) == "group 'invalid' not found"
+
+
+@pytest.mark.skip_if_platform("debian", reason="test is Fedora specific")
+@pytest.mark.skip_if_platform("suse", reason="test is Fedora specific")
+def test_user_group_daemon():
+    # daemon user / group are always defined
+    user = User("daemon")
+    assert user == "daemon"
+    assert user.uid == 2
+    assert user.pgid == 2
+
+    group = Group("daemon")
+    assert group == "daemon"
+    assert group.gid == 2