tools: Let unicode error messages through

[geky]

Some toolchains (GCC) may emit error messages with unicode symbols based on the your localization settings. Instead of being passed to the user as is, the unicode causes an exception.

I'm not sure exactly what the correct fix is regarding python2+3 compat, but changing str to unicode seems to work on my setup (x86_64-linux-gnu-gcc 5.4.0 + python 2.7.12 + mbed-os-5c7cd1f + LANG=en_US.UTF-8)

cc @theotherjimmy

[theotherjimmy]

unicode does not exist in Python 3. Please import it from six or do a try: ... except ImportError: like utils.py

[geky]

Ah, it looks like from builtins import str gets you a unicode compatible str function. @theotherjimmy does this work for you?

[theotherjimmy]

@geky Nope. That returns a str on both python 2 and 3. str is bytes for 2 and unicode for 3. They are not compatible. Turns out that the Python documentation indicates that this is the same as str and IS WRONG.

[geky]

It seems to behave as unicode, even in python2:

$ python2 -c 'from builtins import str; print(str(u"\U0001f60b"))'
$ python3 -c 'from builtins import str; print(str(u"\U0001f60b"))'

This module contains backports the data types that were significantly changed in the transition from Python 2 to Python 3. [Including] an implementation of Python 3’s str object (pure Python subclass of Python 2’s builtin unicode type)

http://python-future.org/reference.html#module-future.builtins

[theotherjimmy]

@geky That website is quite confusing: it seems to indicate that it's describing the python-future package. Are they talking about a competitor to six? or is this builtin?

[theotherjimmy]

Either way, Sure you can use that import. It seems to work. Just take a look at the rest of the file to verify that you're not breaking any other str invocations (I don't think that will)

[geky]

I don't know why it is and it is confusing, but the builtins module (not __builtins__) seems to have all of the python3 builtins for python2.

I tested most of the other str invocations they all should probably have been unicode strings anyways.

[theotherjimmy]

Nice 👍

[theotherjimmy]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 1207
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/6154/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 878
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/6154/

[mbed-ci]

Test : SUCCESS

Build number : 1006
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/6154/1006

[adbridge]

Also reliant on #5848 for 5.8