We check the parameters, and launch the build, if everything is correct

def force(self, owner, builderNames=None, builderid=None, **kwargs):
        """
        We check the parameters, and launch the build, if everything is correct
        """
        builderNames = yield self.computeBuilderNames(builderNames, builderid)
        if not builderNames:
            raise KeyError("builderNames not specified or not supported")

        # Currently the validation code expects all kwargs to be lists
        # I don't want to refactor that now so much sure we comply...
        kwargs = dict((k, [v]) if not isinstance(v, list) else (k, v)
                      for k, v in kwargs.items())

        # probably need to clean that out later as the IProperty is already a
        # validation mechanism
        collector = ValidationErrorCollector()
        reason = yield collector.collectValidationErrors(self.reason.fullName,
                                                         self.reason.getFromKwargs, kwargs)
        if owner is None or owner == "anonymous":
            owner = yield collector.collectValidationErrors(self.username.fullName,
                                                            self.username.getFromKwargs, kwargs)

        properties, changeids, sourcestamps = yield self.gatherPropertiesAndChanges(
            collector, **kwargs)

        collector.maybeRaiseCollectedErrors()

        properties.setProperty("reason", reason, "Force Build Form")
        properties.setProperty("owner", owner, "Force Build Form")

        r = self.reasonString % {'owner': owner, 'reason': reason}

        # turn sourcestamps into a list
        for cb, ss in sourcestamps.items():
            ss['codebase'] = cb
        sourcestamps = list(sourcestamps.values())

        # everything is validated, we can create our source stamp, and
        # buildrequest
        res = yield self.addBuildsetForSourceStampsWithDefaults(
            reason=r,
            sourcestamps=sourcestamps,
            properties=properties,
            builderNames=builderNames,
        )

        return res