publicize end of life for cwltool on Python 2.7 (#1153)

Author: mr-c

cwltool/__init__.py

@@ -1,3 +1,17 @@
 """Reference implementation of the CWL standards."""
 from __future__ import absolute_import
+import warnings
+import sys
 __author__ = '[email protected]'
+
+class CWLToolDeprecationWarning(Warning):
+    pass
+
+# Hate this?
+# set PYTHONWARNINGS=ignore:DEPRECATION::cwltool.__init__
+if sys.version_info < (3, 0):
+    warnings.warn("""
+DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020.
+Please upgrade your Python as the Python 2.7 version of cwltool won't be
+maintained after that date.
+""",  category=CWLToolDeprecationWarning)

cwltool/main.py

@@ -572,7 +572,6 @@ def main(argsl=None,                   # type: List[str]
             if os.path.isfile("CWLFile"):
                 setattr(args, "workflow", "CWLFile")
             else:
-                _logger.error("")
                 _logger.error("CWL document required, no input file was provided")
                 arg_parser().print_help()
                 return 1

setup.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python
 """Setup for the reference implementation of the CWL standards."""
+from __future__ import print_function
 import os
 import sys
 
@@ -19,6 +20,13 @@
 NEEDS_PYTEST = {'pytest', 'test', 'ptr'}.intersection(sys.argv)
 PYTEST_RUNNER = ['pytest-runner', 'pytest-cov'] if NEEDS_PYTEST else []
 
+if sys.version_info < (3, 0):
+    print("""
+DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020.
+Please upgrade your Python as the Python 2.7 version of cwltool won't be
+maintained after that date.
+""", file=sys.stderr)
+
 setup(name='cwltool',
       version='1.0',
       description='Common workflow language reference implementation',