fix imports for 1.14

ml-agents/mlagents/trainers/tf.py

-import logging
-
+import tensorflow as tf
-def warnings_as_errors(log_record):
-    # Raise deprecated warnings as exceptions.
-    if log_record.levelno == logging.WARNING and "deprecated" in log_record.msg:
-        merged = log_record.getMessage()
-        raise RuntimeError(merged)
-    return True
+# TODO better version check, this will do for now though
+is_tf2 = tf.__version__ == "2.0.0"
-
-# TODO only enable this with a environment variable
-if False:
-    logging.getLogger("tensorflow").addFilter(warnings_as_errors)
-
-try:
+if is_tf2:
-except ImportError:
-    import tensorflow as tf
-# TODO better version check, this will do for now though
-is_tf2 = tf.__version__ == "2.0.0"
-if is_tf2:
     tf_variance_scaling = tf.initializers.variance_scaling
     tf_flatten = tf.layers.flatten
     tf_rnn = tf.nn.rnn_cell