Attempt try catch to prevent errors

pytorch_lightning/overrides/fairscale.py

@@ -11,20 +11,24 @@
 # 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.
-
-from fairscale.nn.data_parallel.sharded_ddp import ShardedDataParallel
+try:
+    from fairscale.nn.data_parallel.sharded_ddp import ShardedDataParallel
+except (ModuleNotFoundError, ImportError):
+    FAIRSCALE_SHARDED_AVAILABLE = False
+else:
+    FAIRSCALE_SHARDED_AVAILABLE = True
 
 
-class LightningShardedDataParallel(ShardedDataParallel):
+    class LightningShardedDataParallel(ShardedDataParallel):
 
-    def forward(self, *inputs, **kwargs):
-        if self.enable_broadcast_buffers:
-            self.sync_buffers()
+        def forward(self, *inputs, **kwargs):
+            if self.enable_broadcast_buffers:
+                self.sync_buffers()
 
-        if self.module.training:
-            outputs = self.module.training_step(*inputs, **kwargs)
-        elif self.module.testing:
-            outputs = self.module.test_step(*inputs, **kwargs)
-        else:
-            outputs = self.module.validation_step(*inputs, **kwargs)
-        return outputs
+            if self.module.training:
+                outputs = self.module.training_step(*inputs, **kwargs)
+            elif self.module.testing:
+                outputs = self.module.test_step(*inputs, **kwargs)
+            else:
+                outputs = self.module.validation_step(*inputs, **kwargs)
+            return outputs