open with utf-8 support

[acaire]

Without this fix, pex will raise pex.resolver.Untranslateable due to
non utf-8 characters in setup.py or init.py:

$ pex -r requirements.txt -c foobar -o foobar.pex
**** Failed to install pygments-markdown-lexer-0.1.0.dev39. stdout:

**** Failed to install pygments-markdown-lexer-0.1.0.dev39. stderr:
Traceback (most recent call last):
File "", line 7, in
File "/tmp/virtualenv/lib/python3.4/encodings/ascii.py", line 26, in decode
return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 158: ordinal not in range(128)

Traceback (most recent call last):
File "/tmp/virtualenv/bin/pex", line 11, in
sys.exit(main())
File "/tmp/virtualenv/lib/python3.4/site-packages/pex/bin/pex.py", line 509, in main
pex_builder = build_pex(reqs, options, resolver_options_builder)
File "/tmp/virtualenv/lib/python3.4/site-packages/pex/bin/pex.py", line 471, in build_pex
resolveds = resolver.resolve(resolvables)
File "/tmp/virtualenv/lib/python3.4/site-packages/pex/resolver.py", line 200, in resolve
dist = self.build(package, resolvable.options)
File "/tmp/virtualenv/lib/python3.4/site-packages/pex/resolver.py", line 257, in build
dist = super(CachingResolver, self).build(package, options)
File "/tmp/virtualenv/lib/python3.4/site-packages/pex/resolver.py", line 168, in build
raise Untranslateable('Package %s is not translateable by %s' % (package, translator))
pex.resolver.Untranslateable: Package SourcePackage('file:///root/.pex/build/pygments-markdown-lexer-0.1.0.dev39.zip') is not translateable by ChainedTranslator(WheelTranslator, EggTranslator, SourceTranslator)

[kwlzn]

any reason to not just use io.open here instead? it should be in python 2.6 and up and also supports an encoding= kwarg - and is the default open in python3.

I think you could also avoid the semicolon by using the multiple import syntax at the module level:

...
SETUP_BOOTSTRAP_HEADER = "import io, sys"
...
exec(compile(io.open(..., encoding='utf-8')...
...

[acaire]

I just took this SO question as gospel in terms of speed improvements but admittedly didn't do any benchmarks - I'll push again with io.open

[acaire]

@kwlzn cheers for the feedback - Updated.

[kwlzn]

@acaire merged - thanks for the PR!