[Deprecation] Deprecate python2 as it has reached EOF on Jan 1st, 2020 (

#1141)

* add warning

* fix lint

gluoncv/__init__.py

@@ -9,7 +9,8 @@
 from . import model_zoo
 from . import nn
 from . import utils
-from .utils.version import _require_mxnet_version
+from .utils.version import _require_mxnet_version, _deprecate_python2
 from . import loss
 
+_deprecate_python2()
 _require_mxnet_version('1.4.0')

gluoncv/utils/version.py

@@ -1,7 +1,8 @@
 """Utility functions for version checking."""
+import sys
 import warnings
 
-__all__ = ['check_version', '_require_mxnet_version']
+__all__ = ['check_version', '_require_mxnet_version', '_deprecate_python2']
 
 def check_version(min_version, warning_only=False):
  """Check the version of gluoncv satisfies the provided minimum version.
@@ -35,10 +36,18 @@ def _require_mxnet_version(mx_version):
  "Legacy mxnet-mkl=={} detected, some new modules may not work properly. "
  "mxnet-mkl>={} is required. You can use pip to upgrade mxnet "
  "`pip install mxnet-mkl --pre --upgrade` "
- "or `pip install mxnet-cu90mkl --pre --upgrade`").format(mx.__version__, mx_version)
+ "or `pip install mxnet-cu100mkl --pre --upgrade`\
+ ").format(mx.__version__, mx_version)
  raise ImportError(msg)
  except ImportError:
  raise ImportError(
  "Unable to import dependency mxnet. "
- "A quick tip is to install via `pip install mxnet-mkl/mxnet-cu90mkl --pre`. "
+ "A quick tip is to install via `pip install mxnet-mkl/mxnet-cu100mkl --pre`. "
  "please refer to https://gluon-cv.mxnet.io/#installation for details.")
+
+def _deprecate_python2():
+ if sys.version_info[0] < 3:
+ msg = 'Python2 has reached the end of its life on January 1st, 2020. ' + \
+ 'A future version of gluoncv will drop support for Python 2.'
+ warnings.simplefilter('always', DeprecationWarning)
+ warnings.warn(msg, DeprecationWarning)