This is a port of the code from slapos.toolbox for future
   replacement.

There is now `EmptyResult` object which is an empty promise result. This result is send if the promise test or anomaly was skiped (if disabled).
To prevent raise because `EmptyResult` is unknonwn on old slapos-node with `slapos.core < 1.4.17` we will send an empty TestResult instead.

Support for promise test-less or anomaly-less allow to disable either the test phase or the anomaly phase.

by default, test and anomaly are enabled. Test will run when buildout is processing the computer partition, and anomaly when the partition is processed.

Call `self.setTestLess()` in __init__.py of the promise will disable Test and set `__is_tested = False`. Call `self.setAnomalyLess()` will rather disable Anomaly and set `__is_anomaly_detected = False`.

If the promise is test less, then slapgrid will not run the promise while processing the partition which mean that the promise will not report error, only Anomaly will be checked. Samething, if promise is anomaly less, only test will run when slapgrid is processing the partition.

Add ofset +0000 to utc date so after convert to another timezone it still remain valid.

/reviewed-on !63

if the message size is too big, the promise process can hang on queue.put and parent process will no be able to read the message.
This will finally result in a deadlock situation.

To allow promises to update thier sys.path and import needed dependencies,
module load is now moved to PromiseProcess class. This prevent promises to modify
sys.path of parent process.

python promises can define sense, test and anomaly method.
test method will be called by slapgrid or when no bang is needed for the promise anomaly method is
called when a promise failure required to bang the master, anomaly method can be optional but it's not the case for test method.

Slapgrid always run promises and save the result in .slapgrid/promise/result in a JSON format. The result will be used later by monitor
When a partition is correctly deployed, slapgrid will only run promise anomaly and will bang if there is an error and if the failed promise can bang

check promise anomaly when partition is upto date