add mxnet version check (#301)

* add mxnet version check

* fix lint

* correct version

* fix import order

gluoncv/__init__.py

@@ -1,7 +1,26 @@
 # coding: utf-8
+# pylint: disable=wrong-import-position
 """GluonCV: a deep learning vision toolkit powered by Gluon."""
 from __future__ import absolute_import
 
+# mxnet version check
+mx_version = '1.3.0'
+try:
+ import mxnet as mx
+ import warnings
+ from distutils.version import LooseVersion
+ if LooseVersion(mx.__version__) < LooseVersion(mx_version):
+ msg = (
+ "Legacy mxnet=={} detected, some new modules may not work properly. "
+ "mxnet>={} is recommended. You can use pip to upgrade mxnet "
+ "`pip install mxnet --pre --upgrade`").format(mx.__version__, mx_version)
+ warnings.warn(msg)
+except ImportError:
+ raise ImportError(
+ "Unable to import dependency mxnet. "
+ "A quick tip is to install via `pip install mxnet --pre`. "
+ "please refer to https://gluon-cv.mxnet.io/#installation for details.")
+
 __version__ = '0.3.0'
 
 from . import data