Created exception module for unitytrainers.

python/tests/test_unitytrainers.py

 from unitytrainers.models import *
 from unitytrainers.ppo.trainer import PPOTrainer
 from unitytrainers.bc.trainer import BehavioralCloningTrainer
-from unitytrainers import Curriculum
-from unityagents import UnityEnvironmentException
+from unitytrainers.curriculum import Curriculum
+from unitytrainers.exception import CurriculumError
+from unityagents.exception import UnityEnvironmentException
 from .mock_communicator import MockCommunicator
 
 dummy_start = '''{
         with mock.patch(open_name, create=True) as mock_open:
             mock_open.return_value = 0
             mock_load.return_value = bad_curriculum
-            with pytest.raises(UnityEnvironmentException):
+            with pytest.raises(CurriculumError):
-            with pytest.raises(UnityEnvironmentException):
+            with pytest.raises(CurriculumError):
                 Curriculum('tests/test_unityagents.py', {"param1": 1, "param2": 1})
             curriculum = Curriculum('tests/test_unityagents.py', {"param1": 1, "param2": 1, "param3": 1})
             assert curriculum.get_lesson_number == 0

python/unitytrainers/__init__.py

 from .bc.trainer import *
 from .ppo.models import *
 from .ppo.trainer import *
+from .exception import *

python/unitytrainers/curriculum.py

 import json
 
-from unityagents.exception import UnityEnvironmentException
+from .exception import CurriculumError
 
 import logging
 
                 with open(location) as data_file:
                     self.data = json.load(data_file)
             except IOError:
-                raise UnityEnvironmentException(
+                raise CurriculumError(
-                raise UnityEnvironmentException("There was an error decoding {}".format(location))
+                raise CurriculumError("There was an error decoding {}".format(location))
-                    raise UnityEnvironmentException("{0} does not contain a "
+                    raise CurriculumError("{0} does not contain a "
                                                     "{1} field.".format(location, key))
             parameters = self.data['parameters']
             self.measure_type = self.data['measure']
-                    raise UnityEnvironmentException(
+                    raise CurriculumError(
-                    raise UnityEnvironmentException(
+                    raise CurriculumError(
                         "The parameter {0} in Curriculum {1} must have {2} values "
                         "but {3} were found".format(key, location,
                                                     self.max_lesson_number + 1, len(parameters[key])))

python/unitytrainers/exception.py

+"""
+Contains exceptions for the unitytrainers package.
+"""
+
+class TrainerError(Exception):
+    """
+    Any error related to the trainers in the ML-Agents Toolkit.
+    """
+    pass
+
+class CurriculumError(TrainerError):
+    """
+    Any error related to training with a curriculum.
+    """
+    pass