b423292cd0
The release of pip10 has shown up a few issues here Firstly, pip10 now refuses to overwrite distutils installed packages, which includes "python-virtualenv" on centos. History has shown us that we want the packages installed and overwritten, to avoid the packages coming back and messing things up. Pre-install all the packages, then list the files in the packages with "rpm" directly and remove them. This way pip is happy to install. We need to take better account of the package names for this; on Fedora things have switch to "python2-virtualenv" instead of "python-virtualenv" and we can't use an alias to list the package contents. This also highlighted that python2-pip is in EPEL for centos, so enable that when we install it. Make the epel element a no-op for non centos/rhe distros. There is a related change in recent fedora that python3 now installs binaries into /usr/local/bin. There are commented swizzles in here to ensure we retain the status quo of "pip" and "virtualenv" both being python2 based, with the python3 versions being called explicitly "pip3" and "virtualenv3" respectively. Change-Id: I2ffdd9f615ae6b00428c17249e4f216774991b99
pip-and-virtualenv
This element installs pip and virtualenv in the image.
Note
This element setups and Python 2 and Python 3 environment. This means it will bring in python2 packages, so isn't appropriate if you want a python3 only environment.
Package install
If the package installtype is used then these programs are installed
from distribution packages. In this case, pip and
virtualenv will be installed only for the python
version identified by dib-python (i.e. the default python
for the platform).
Distribution packages have worked out name-spacing such that only
python2 or python3 owns common scripts like /usr/bin/pip
(on most platforms, pip refers to python2 pip, and
pip3 refers to python3 pip, although some may choose the
reverse).
To install pip and virtualenv from package:
export DIB_INSTALLTYPE_pip_and_virtualenv=packageSource install
Source install is the default. If the source installtype is used,
pip and virtualenv are installed from the
latest upstream releases.
Source installs from these tools are not name-spaced. It is
inconsistent across platforms if the first or last install gets to own
common scripts like /usr/bin/pip and
virtualenv.
To avoid inconsistency, we firstly install the packaged python 2
and 3 versions of pip and
virtualenv. This prevents a later install of these
distribution packages conflicting with the source install. We then
overwrite pip and virtualenv via
get-pip.py and pip respectively.
The system will be left in the following state:
/usr/bin/pip: python2 pip/usr/bin/pip2: python2 pip (same as prior)/usr/bin/pip3: python3 pip/usr/bin/virtualenv: python2 virtualenv
(note python3 virtualenv script is not
installed, see below)
Source install is supported on limited platforms. See the code, but this includes Ubuntu and RedHat platforms.
Using the tools
Due to the essentially unsolvable problem of "who owns the script",
it is recommended to not call pip or
virtualenv directly. You can directly call them with the
-m argument to the python interpreter you wish to install
with.
For example, to create a python3 environment do:
# python3 -m virtualenv myenv
# myenv/bin/pip install mytoolTo install a python2 tool from pip:
# python2 -m pip install mytoolIn this way, you can always know which interpreter is being used (and affected by) the call.
Ordering
Any element that uses these commands must be designated as 05-* or higher to ensure that they are first installed.