Ineffectual assignments are assignments that don't matter and typically
involve missing usage of information that was obtained but not used. The
compiler does not reject such code but it can lead to real problems,
mainly on assigning to `err` and then not checking it before `err` is
re-assigned.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>