id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
15405	Firefox-91 and thunderbird: replace create-mach-environment	ken@…	ken@…	"Joe Locash told me that create-mach-environment downloads packages, and therefore prevents him compiling firefox while he is offline. Instead, he exports MACH_USE_SYSTEM_PYTHON=1 and similarly prepends that to the install.

I had assumed that using this would download into the system python using pip.

In a build with create-mach-environment the relevant lines of my log are:
{{{
 created virtual environment CPython3.9.6.final.0-64 in 136ms
  creator CPython3Posix(dest=/scratch/working/firefox-91.0/mozbuild/_virtualenvs/mach, clear=False, no_vcs_ignore=False, global=False)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/root/.local/share/virtualenv)
    added seed packages: pip==20.3.1, setuptools==51.0.0, wheel==0.36.1
  activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator
Collecting psutil==5.8.0
  Downloading psutil-5.8.0-cp39-cp39-manylinux2010_x86_64.whl (293 kB)
Installing collected packages: psutil
Successfully installed psutil-5.8.0
Collecting zstandard==0.15.2
  Downloading zstandard-0.15.2-cp39-cp39-manylinux2014_x86_64.whl (2.2 MB)
Installing collected packages: zstandard
Successfully installed zstandard-0.15.2
Collecting appdirs==1.4.4
  Downloading appdirs-1.4.4-py2.py3-none-any.whl (9.6 kB)
Collecting attrs==20.3.0
  Downloading attrs-20.3.0-py2.py3-none-any.whl (49 kB)
Collecting cffi==1.14.4
  Downloading cffi-1.14.4-cp39-cp39-manylinux1_x86_64.whl (405 kB)
Collecting click==7.1.2
  Downloading click-7.1.2-py2.py3-none-any.whl (82 kB)
}}}
and a lot more of the same.

Using MACH_USE_SYSTEM_PYTHON=1 the relevant lines are:
{{{
 0:00.39 /usr/bin/python3 /scratch/working/firefox-91.0/configure.py
 0:00.48 Creating Python 3 environment
 0:00.75 created virtual environment CPython3.9.6.final.0-64 in 142ms
 0:00.75   creator CPython3Posix(dest=/scratch/working/firefox-91.0/firefox-build-dir/_virtualenvs/common, clear=False, no_vcs_ignore=False, global=False)
 0:00.75   seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/root/.local/share/virtualenv)
 0:00.75     added seed packages: pip==20.3.1, setuptools==51.0.0, wheel==0.36.1
 0:00.75   activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator 
 0:00.82 Re-executing in the virtualenv
}}}

with no downloads.
"	enhancement	closed	normal	11.0	BOOK	git	medium	fixed