Node preemptability is determined inconsistently
The batch system looks for a text value for preemptability while the cluster scaler code looks for a scalar value.
diff --git a/src/toil/batchSystems/mesos/batchSystem.py b/src/toil/batchSystems/mesos/batchSystem.py
index 93c03468..38902e39 100644
--- a/src/toil/batchSystems/mesos/batchSystem.py
+++ b/src/toil/batchSystems/mesos/batchSystem.py
@@ -437,7 +437,7 @@ class MesosBatchSystem(BatchSystemSupport,
             preemptable = False
             for attribute in offer.attributes:
                 if attribute.name == 'preemptable':
-                    preemptable = bool(attribute.scalar.value)
+                    preemptable = strict_bool(attribute.text.value)
             if preemptable:
                 try:
                     self.nonPreemptibleNodes.remove(offer.slave_id.value)
['src/toil/batchSystems/mesos/batchSystem.py']