SCons: Fix Python 2 support after #43057

[akien-mga]

That's not a very pretty way to parse a string from a python file
though, there should definitely be cleaner and more reliable ways
to do this without using exec().

[Xrayez]

That's what SCons does while parsing Python scripts. It's not reliable to import those files with sys.path.insert(0, tmppath), it would definitely require more finicky ways to make it work with custom modules which may reside virtually anywhere on your filesystem. I've actually tried this approach first, but with no success unfortunately.

There might be better ways to do this, not denying that. 🙂

[akien-mga]

Found a slightly nicer way in https://stackoverflow.com/a/56800610.

[Xrayez]

I haven't used execfile because it's not supported by Python 3.x, which #43057 targeted. https://stackoverflow.com/questions/436198/what-is-an-alternative-to-execfile-in-python-3

[akien-mga]

Ah indeed, I had tested it with Python 3 but without actually making use of that code.

So back to:

exec(f.read(), version) in locals()

which seems to work.

That being said, with or without that fix, I'm getting:

$ scons p=x11 -j7 custom_modules=..
/usr/bin/scons p=x11 -j7 custom_modules=.. 2>&1 | tee -a build.log
scons: Reading SConscript files ...
  File "<string>", line 107
    raise ValueError, "invalid version number '%s'" % vstring
                    ^
SyntaxError: invalid syntax

Same error on the master branch.

[akien-mga]

Superseded by #45901.