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