b8ad9c2e37
On a system where the packaged pip/virtualenv is up-to-date with upstream (such as Fedora 26 ... for now), we don't reinstall, which then violates a bunch of assumptions later on. Force install. Change-Id: I6ebcda0351997fa7e32f0e6e77a98b2c33764e3f
pip-and-virtualenv
This element installs pip and virtualenv in the image.
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.