minor fix: incorrect assert string message formatting (#631)

* do not split strings so that format() works as expected

* address flake8 indentation issue

.gitignore

@@ -25,6 +25,9 @@ dist/
 # Pycharm editor settings
 .idea
 
+# MacOS
+.DS_Store
+
 # project dirs
 /datasets
 /models

maskrcnn_benchmark/data/build.py

@@ -110,17 +110,17 @@ def make_data_loader(cfg, is_train=True, is_distributed=False, start_iter=0):
         images_per_batch = cfg.SOLVER.IMS_PER_BATCH
         assert (
             images_per_batch % num_gpus == 0
-        ), "SOLVER.IMS_PER_BATCH ({}) must be divisible by the number "
-        "of GPUs ({}) used.".format(images_per_batch, num_gpus)
+        ), "SOLVER.IMS_PER_BATCH ({}) must be divisible by the number of GPUs ({}) used.".format(
+            images_per_batch, num_gpus)
         images_per_gpu = images_per_batch // num_gpus
         shuffle = True
         num_iters = cfg.SOLVER.MAX_ITER
     else:
         images_per_batch = cfg.TEST.IMS_PER_BATCH
         assert (
             images_per_batch % num_gpus == 0
-        ), "TEST.IMS_PER_BATCH ({}) must be divisible by the number "
-        "of GPUs ({}) used.".format(images_per_batch, num_gpus)
+        ), "TEST.IMS_PER_BATCH ({}) must be divisible by the number of GPUs ({}) used.".format(
+            images_per_batch, num_gpus)
         images_per_gpu = images_per_batch // num_gpus
         shuffle = False if not is_distributed else True
         num_iters = None