Update python2 to newer version on mac

Update python2 to newer version on mac as builds fail due to too old version of python which uses unsupported tlsv1 version(wont connect to github).

Running configuration tests...
agent:2019/04/05 13:56:29 build.go:197: Checking for valid makespec...
agent:2019/04/05 13:56:29 build.go:197: + cd /Users/qt/work/qt/qtbase/config.tests/verifyspec && /Users/qt/work/qt/qtbase/bin/qmake "CONFIG -= qt debug_and_release app_bundle lib_bundle" "CONFIG += static warn_off console single_arch" -early "CONFIG += cross_compile" /Users/qt/work/qt/qtbase/config.tests/verifyspec
agent:2019/04/05 13:56:30 build.go:197: > Info: creating stash file /Users/qt/work/qt/qtbase/config.tests/.qmake.stash
agent:2019/04/05 13:56:30 build.go:197: + cd /Users/qt/work/qt/qtbase/config.tests/verifyspec && MAKEFLAGS= /usr/bin/make
agent:2019/04/05 13:56:30 build.go:197: > em++ -c -pipe -s USE_FREETYPE=1 -s USE_ZLIB=1 -O3 -std=gnu++11 -w -I. -I/Users/qt/.emscripten_ports/openssl/include -I/Users/qt/work/qt/qtbase/mkspecs/wasm-emscripten -o verifyspec.o verifyspec.cpp
agent:2019/04/05 13:56:30 build.go:197: > root:WARNING: retrieving port: zlib from https://github.com/emscripten-ports/zlib/archive/version_1.zip
agent:2019/04/05 13:56:30 build.go:197: > Traceback (most recent call last):
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/emcc.py", line 3153, in <module>
agent:2019/04/05 13:56:30 build.go:197: > sys.exit(run())
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/emcc.py", line 1608, in run
agent:2019/04/05 13:56:30 build.go:197: > compile_source_file(i, input_file)
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/emcc.py", line 1593, in compile_source_file
agent:2019/04/05 13:56:30 build.go:197: > args = get_clang_args([input_file]) + ['-c', '-o', output_file]
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/emcc.py", line 1574, in get_clang_args
agent:2019/04/05 13:56:30 build.go:197: > args = system_libs.process_args(args, shared.Settings)
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/tools/system_libs.py", line 1004, in process_args
agent:2019/04/05 13:56:30 build.go:197: > args = port.process_args(Ports, args, settings, shared)
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/tools/ports/zlib.py", line 47, in process_args
agent:2019/04/05 13:56:30 build.go:197: > get(ports, settings, shared)
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/tools/ports/zlib.py", line 13, in get
agent:2019/04/05 13:56:30 build.go:197: > ports.fetch_project('zlib', 'https://github.com/emscripten-ports/zlib/archive/' + TAG + '.zip', 'zlib-' + TAG)
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/tools/system_libs.py", line 903, in fetch_project
agent:2019/04/05 13:56:30 build.go:197: > retrieve()
agent:2019/04/05 13:56:30 build.go:197: > File "/opt/emsdk/emscripten-1.38.27/tools/system_libs.py", line 867, in retrieve
agent:2019/04/05 13:56:30 build.go:197: > f = urlopen(url)
agent:2019/04/05 13:56:30 build.go:197: > File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 154, in urlopen
agent:2019/04/05 13:56:30 build.go:197: > return opener.open(url, data, timeout)
agent:2019/04/05 13:56:30 build.go:197: > File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 429, in open
agent:2019/04/05 13:56:30 build.go:197: > response = self._open(req, data)
agent:2019/04/05 13:56:30 build.go:197: > File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 447, in _open
agent:2019/04/05 13:56:30 build.go:197: > '_open', req)
agent:2019/04/05 13:56:30 build.go:197: > File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 407, in _call_chain
agent:2019/04/05 13:56:30 build.go:197: > result = func(*args)
agent:2019/04/05 13:56:30 build.go:197: > File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 1241, in https_open
agent:2019/04/05 13:56:30 build.go:197: > context=self._context)
agent:2019/04/05 13:56:30 build.go:197: > File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 1198, in do_open
agent:2019/04/05 13:56:30 build.go:197: > raise URLError(err)
agent:2019/04/05 13:56:30 build.go:197: > urllib2.URLError: <urlopen error [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:661)>
agent:2019/04/05 13:56:30 build.go:197: > make: *** [verifyspec.o] Error 1
agent:2019/04/05 13:56:30 build.go:197: ERROR: Cannot compile a minimal program. The toolchain or QMakeSpec is broken.
agent:2019/04/05 13:56:30 build.go:241: Process finished with error: exit status 3
agent:2019/04/05 13:56:30 build.go:535: Executing scheduled instruction 1 of 1 - Upload all core dumps if there are some