v79.0-1 #5: python >= 3.5 for deb/xenial build

binary_tarball/scripts/3_Configure_Source_Code.sh

@@ -111,6 +111,7 @@ END
 fi
 
 # hopefully the magic sauce that makes things build on 16.04 and later on work "everywhere":
+patch -p1 -i "${CI_PROJECT_DIR}/deb_patches/lower-python3-requirement.patch"
 patch -p1 -i "${CI_PROJECT_DIR}/deb_patches/armhf-reduce-linker-memory-use.patch"
 patch -p1 -i "${CI_PROJECT_DIR}/deb_patches/build-with-libstdc++-7.patch"
 patch -p1 -i "${CI_PROJECT_DIR}/deb_patches/fix-armhf-webrtc-build.patch"

deb_patches/lower-python3-requirement.patch

@@ -0,0 +1,68 @@
+# Revert 6700a8dfaeb1e303955acc05dabd245b9ae3c97e
+
+Bug 1622963 - Require python 3.6 for the build system. r=firefox-build-system-reviewers,rstewart
+
+Differential Revision: https://phabricator.services.mozilla.com/D77754
+
+diff -r ede1c973aa85 build/moz.configure/init.configure
+--- a/build/moz.configure/init.configure	Sun Jun 14 02:41:45 2020 +0000
++++ b/build/moz.configure/init.configure	Sun Jun 14 19:10:48 2020 +0200
+@@ -237,7 +237,7 @@
+ # Python 3
+ # ========
+ 
+-option(env='PYTHON3', nargs=1, help='Python 3 interpreter (3.6 or later)')
++option(env='PYTHON3', nargs=1, help='Python 3 interpreter (3.5 or later)')
+ 
+ 
+ @depends('PYTHON3', check_build_environment, mozconfig, '--help')
+@@ -334,20 +334,20 @@
+                                   '(%s): %s' % (python, e))
+     else:
+         # Fall back to the search routine.
+-        python, version = find_python3_executable(min_version='3.6.0')
++        python, version = find_python3_executable(min_version='3.5.0')
+ 
+         # The API returns a bytes whereas everything in configure is unicode.
+         if python:
+             python = ensure_text(python)
+ 
+     if not python:
+-        raise FatalCheckError('Python 3.6 or newer is required to build. '
++        raise FatalCheckError('Python 3.5 or newer is required to build. '
+                               'Ensure a `python3.x` executable is in your '
+                               'PATH or define PYTHON3 to point to a Python '
+-                              '3.6 executable.')
++                              '3.5 executable.')
+ 
+-    if version < (3, 6, 0):
+-        raise FatalCheckError('Python 3.6 or newer is required to build; '
++    if version < (3, 5, 0):
++        raise FatalCheckError('Python 3.5 or newer is required to build; '
+                               '%s is Python %d.%d' % (python, version[0],
+                                                       version[1]))
+ 
+diff -r ede1c973aa85 python/mozbuild/mozbuild/pythonutil.py
+--- a/python/mozbuild/mozbuild/pythonutil.py	Sun Jun 14 02:41:45 2020 +0000
++++ b/python/mozbuild/mozbuild/pythonutil.py	Sun Jun 14 19:10:48 2020 +0200
+@@ -45,7 +45,7 @@
+ def _find_python_executable(major):
+     if major not in (2, 3):
+         raise ValueError('Expected a Python major version of 2 or 3')
+-    min_versions = {2: '2.7.0', 3: '3.6.0'}
++    min_versions = {2: '2.7.0', 3: '3.5.0'}
+ 
+     def ret(min_version=min_versions[major]):
+         from mozfile import which
+diff -r ede1c973aa85 python/mozbuild/mozbuild/virtualenv.py
+--- a/python/mozbuild/mozbuild/virtualenv.py	Sun Jun 14 02:41:45 2020 +0000
++++ b/python/mozbuild/mozbuild/virtualenv.py	Sun Jun 14 19:10:48 2020 +0200
+@@ -687,7 +687,7 @@
+     major, minor, micro = sys.version_info[:3]
+     minimum_python_versions = {
+         2: LooseVersion('2.7.3'),
+-        3: LooseVersion('3.6.0'),
++        3: LooseVersion('3.5.0'),
+     }
+     our = LooseVersion('%d.%d.%d' % (major, minor, micro))
+