Resolve "Discontinue Python 2.7 support?": Bilby is now python3.5+

.gitlab-ci.yml

@@ -35,11 +35,6 @@ stages:
           ${script} --help;
       done
 
-# test basic setup on python2
-basic-2.7:
-  <<: *test-python
-  image: python:2.7
-
 # test basic setup on python3
 basic-3.7:
   <<: *test-python

bilby/__init__.py

@@ -17,6 +17,7 @@ https://lscsoft.docs.ligo.org/bilby/installation.html.
 
 
 from __future__ import absolute_import
+import sys
 
 from . import core, gw, hyper
 
@@ -25,3 +26,25 @@ from .core.sampler import run_sampler
 from .core.likelihood import Likelihood
 
 __version__ = utils.get_version_information()
+
+
+if sys.version_info < (3,):
+    raise ImportError(
+"""You are running bilby 0.6.4 on Python 2
+
+Bilby 0.6.4 and above are no longer compatible with Python 2, and you still
+ended up with this version installed. That's unfortunate; sorry about that.
+It should not have happened. Make sure you have pip >= 9.0 to avoid this kind
+of issue, as well as setuptools >= 24.2:
+
+ $ pip install pip setuptools --upgrade
+
+Your choices:
+
+- Upgrade to Python 3.
+
+- Install an older version of bilby:
+
+ $ pip install 'bilby<0.6.4'
+
+""")

docs/installation.txt

@@ -10,7 +10,7 @@ Installation
 
           $ conda install -c conda-forge bilby
 
-      Supported python versions: 2.7, 3.5+.
+      Supported python versions: 3.5+.
 
    .. tab:: Pip
 
@@ -18,7 +18,7 @@ Installation
 
           $ pip install bilby
 
-      Supported python versions: 2.7, 3.5+.
+      Supported python versions: 3.5+.
 
 
 This will install all requirements for running :code:`bilby` for general
@@ -47,7 +47,7 @@ wave inference, please additionally run the following commands.
 Install bilby from source
 -------------------------
 
-:code:`bilby` is developed and tested with both Python 2.7+ and Python 3.7+. In the
+:code:`bilby` is developed and tested with Python 3.6+. In the
 following, we assume you have a working python installation, `python pip
 <https://packaging.python.org/tutorials/installing-packages/#use-pip-for-installing)>`_,
 and `git <https://git-scm.com/>`_. See :ref:`installing-python` for our
@@ -60,7 +60,7 @@ Clone the repository, install the requirements, and then install the software:
    $ git clone git@git.ligo.org:lscsoft/bilby.git
    $ cd bilby/
    $ pip install -r requirements.txt
-   $ python setup.py install
+   $ pip install .
 
 Once you have run these steps, you have :code:`bilby` installed. You can now
 try to run the examples.
@@ -79,6 +79,13 @@ try to run the examples.
 
       $ git clone https://git.ligo.org/lscsoft/bilby.git
 
+.. note::
+   You may be use to using :code:`$ python setup.py install` to install software
+   from source. While it is possible to do this, current recommentations from
+   the python community (see, e.g. `this site <https://python3statement.org/practicalities/>`_
+   are to use :code:`pip`. For development install, the :code:`-e` flag can be
+   used.
+
 Installing optional requirements
 ================================
 

setup.py

@@ -2,8 +2,15 @@
 
 from setuptools import setup
 import subprocess
+import sys
 import os
 
+# check that python version is 3.5 or above
+python_version = sys.version_info
+if python_version < (3, 5):
+    sys.exit("Python < 3.5 is not supported, aborting setup")
+print("Confirmed Python version {}.{}.{} >= 3.5.0".format(*python_version[:3]))
+
 
 def write_version_file(version):
     """ Writes a file with version information to be used at run time
@@ -77,6 +84,7 @@ setup(name='bilby',
       package_data={'bilby.gw': ['prior_files/*'],
                     'bilby.gw.detector': ['noise_curves/*.txt', 'detectors/*'],
                     'bilby': [version_file]},
+      python_requires='>=3.5',
       install_requires=[
           'future',
           'dynesty>=1.0.0',
@@ -94,7 +102,7 @@ setup(name='bilby',
                      'bilby_convert_resume=cli_bilby.resume:main']
                     },
       classifiers=[
-          "Programming Language :: Python :: 2.7",
+          "Programming Language :: Python :: 3.6",
           "Programming Language :: Python :: 3.7",
           "License :: OSI Approved :: MIT License",
           "Operating System :: OS Independent"])