Implement non-strict mode

[renskiy]

Non-stric mode is mode when attempting to get/set value from/to local instance silently ignores lack of the current task and doesn't raise RuntimeError. I think its very useful to have such mode.

[vkryachko]

Hi @renskiy,

Thanks for you interest in the library.

From what I understand you want to have a tasklocal that is valid outside a task. I think it is dangerous and harmful as it can lead to subtle and hard-to-track bugs.
That's why I intentionally made it so that the tasklocal fails loud and early instead of silently swallowing the error and returning a global dict which can be a problem in itself as it is not thread-safe.

Can you elaborate a bit more as to why you think it would be useful and what your use-case is?

[renskiy]

@vkryachko, yes this can be dangerous and because of it strict mode is enabled by default.

My use-case is following:

class MyTaskLocals(tasklocals.local):
    def __init__(**kwargs):
        self.foo = 'bar'

Trying to get instance of this class outside of the task leads to RuntimeError