chore: import upstream snapshot with attribution

nemo/utils/exceptions.py

@@ -0,0 +1,41 @@
+# Copyright (c) 2020, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class NeMoBaseException(Exception):
+    """NeMo Base Exception. All exceptions created in NeMo should inherit from this class"""
+
+
+class LightningNotInstalledException(NeMoBaseException):
+    """Raised when optional Lightning dependencies are required but unavailable."""
+
+    def __init__(self, obj):
+        message = (
+            f" You are trying to use {obj} without installing all of pytorch_lightning, hydra, and "
+            f"omegaconf. Please install those packages before trying to access {obj}."
+        )
+        super().__init__(message)
+
+
+class CheckInstall:
+    """Placeholder that raises when optional Lightning dependencies are missing."""
+
+    def __init__(self, *args, **kwargs):
+        raise LightningNotInstalledException(self)
+
+    def __call__(self, *args, **kwargs):
+        raise LightningNotInstalledException(self)
+
+    def __getattr__(self, *args, **kwargs):
+        raise LightningNotInstalledException(self)