Merge pull request #9900 from Carreau/update-no-2x

Improve our error messages for non compatibility.

IPython/__init__.py

@@ -22,17 +22,24 b' from __future__ import absolute_import'
 
 import os
 import sys
-import warnings
 
 #-----------------------------------------------------------------------------
 # Setup everything
 #-----------------------------------------------------------------------------
 
 # Don't forget to also update setup.py when this changes!
-v = sys.version_info
-if v[:2] < (3,3):
-    raise ImportError('IPython requires Python version 3.3 or above.')
-del v
+if sys.version_info < (3,3):
+    raise ImportError(
+"""
+IPython 6.0+ does not support Python 2.6, 2.7, 3.0, 3.1, or 3.2.
+When using Python 2.7, please install IPython 5.x LTS Long Term Support version.
+Beginning with IPython 6.0, Python 3.3 and above is required.
+
+See IPython `README.rst` file for more information:
+
+    https://github.com/ipython/ipython/blob/master/README.rst
+
+""")
 
 # Make it easy to import extensions - they are always directly on pythonpath.
 # Therefore, non-IPython modules can be added to extensions directory.
@@ -143,4 +150,3 b' def start_kernel(argv=None, **kwargs):'
     """
     from IPython.kernel.zmq.kernelapp import launch_new_instance
     return launch_new_instance(argv=argv, **kwargs)
-    

README.rst

@@ -36,16 +36,52 b' Development and Instant runnimg'
 ================================
 
 You can find the latest version of the development documentation on `readthedocs
-<http://ipython.readthedocs.io/en/latest/>`_. 
+<http://ipython.readthedocs.io/en/latest/>`_.
 
 You can run IPython from this directory without even installing it system-wide
 by typing at the terminal::
-    
+
    $ python -m IPython
 
 Or see the `development installation docs
 <http://ipython.readthedocs.io/en/latest/install/install.html#installing-the-development-version>`_
-for the latest revision on read the docs. 
+for the latest revision on read the docs.
 
 Documentation and installation instructions for older version of IPython can be
 found on the `IPython website <http://ipython.org/documentation.html>`_
+
+
+
+IPython requires Python version 3 or above
+==========================================
+
+Starting with version 6.0, IPython does not support Python 2.7, 3.0, 3.1, or
+3.2.
+
+For a version compatible with Python 2.7, please install the 5.x LTS Long Term
+Support version.
+
+If you are encountering this error message you are likely trying to install or
+use IPython from source. You need to checkout the remote 5.x branch. If you are
+using git the following should work:
+
+  $ git fetch origin
+  $ git checkout -b origin/5.x
+
+If you encounter this error message with a regular install of IPython, then you
+likely need to update your package manager, for example if you are using `pip`
+check the version of pip with
+
+  $ pip --version
+
+You will need to update pip to the version 8.2 or greater. If you are not using
+pip, please inquiry with the maintainers of the package for your package
+manager.
+
+For more information see one of our blog posts:
+
+    http://blog.jupyter.org/2016/07/08/ipython-5-0-released/
+
+As well as the following Pull-Request for discussion:
+
+    https://github.com/ipython/ipython/pull/9900

setup.py

@@ -26,9 +26,18 b' import sys'
 
 # This check is also made in IPython/__init__, don't forget to update both when
 # changing Python version requirements.
-v = sys.version_info
-if v[:2] < (3,3):
-    error = "ERROR: IPython requires Python version 3.3 or above."
+if sys.version_info < (3,3):
+    error = """
+IPython 6.0+ does not support Python 2.6, 2.7, 3.0, 3.1, or 3.2.
+When using Python 2.7, please install IPython 5.x LTS Long Term Support version.
+Beginning with IPython 6.0, Python 3.3 and above is required.
+
+See IPython `README.rst` file for more information:
+
+    https://github.com/ipython/ipython/blob/master/README.rst
+
+"""
+
     print(error, file=sys.stderr)
     sys.exit(1)