[build_support] Fixed python 3 errors

[harlanhaskins]

What's in this pull request?

Fixes python3 errors with the build support module
All tests now pass on python3.5 and python2.7

Resolved bug number: N/A Addresses this comment

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[harlanhaskins]

@swift-ci please test

[harlanhaskins]

@RLovelett This should address your python3 issues.
Another issue is that subprocess.check_output() returns bytes in python3, which broke our tests.

[harlanhaskins]

@practicalswift Anything you think I'm missing here?

[practicalswift]

@harlanhaskins LGTM :-)

[harlanhaskins]

@practicalswift Thanks for looking! 😄

[harlanhaskins]

@swift-ci please Python lint

[harlanhaskins]

Thanks @practicalswift and @RLovelett!

[RLovelett]

I'm really sorry I was not able to get here sooner. Unfortunately this did not resolve the issue I reported #1586. Some line number shifted but the error is still largely the same.

Traceback (most recent call last):
  File "utils/build-script", line 1172, in <module>
    sys.exit(main())
  File "utils/build-script", line 1168, in main
    return main_normal()
  File "utils/build-script", line 1028, in main_normal
    xcrun_toolchain=args.darwin_xcrun_toolchain)
  File "utils/swift_build_support/swift_build_support/toolchain.py", line 133, in host_clang
    suffixes=['', '-3.8', '-3.7', '-3.6', '-3.5'])
  File "utils/swift_build_support/swift_build_support/toolchain.py", line 110, in host_toolchain
    return _first_common_toolchain(tools, suffixes=suffixes)
  File "utils/swift_build_support/swift_build_support/toolchain.py", line 72, in _first_common_toolchain
    for name, tool in tools.iteritems():
AttributeError: 'dict' object has no attribute 'iteritems'

Again this is my fault. I should have been more responsive to give the feeback before the merge of this.

I'll see what I can come up with and then submit a PR to resolve it and link back to here for tracability. @harlanhaskins thanks for even looking into this.

[harlanhaskins]

Nope, my fault for not catching that as well. Could you try again with latest master?

[RLovelett]

75de4fe does the trick.

Thank you. 🙇

[harlanhaskins]

Thank you for reporting!

Aside, I feel like we should probably standardize on python3. It's not too difficult to require python3 as a dependency for building Swift, and I'm personally not a fan of keeping python2 around longer.

[RLovelett]

You have my vote to switch to python3.

It might be a hallow victory though because I think swift-lldb (or rather just LLDB) relies on Python 2. All that having been said, swift-lldb usually is just merging in upstream changes. Meaning that switching this over to Python 3 it would have reduced the maintained Python 2 code. I digress.