py3: use native string for 'macosx_app'

I couldn't find any definitive information on this, but all examples
(except for ours) seem to use a native string.

Differential Revision: https://phab.mercurial-scm.org/D7414

mercurial/util.py

@@ -1823,7 +1823,7 b' def pathto(root, n1, n2):'
 
 
 # the location of data files matching the source code
-if procutil.mainfrozen() and getattr(sys, 'frozen', None) != b'macosx_app':
+if procutil.mainfrozen() and getattr(sys, 'frozen', None) != 'macosx_app':
     # executable version (py2exe) doesn't support __file__
     datapath = os.path.dirname(pycompat.sysexecutable)
 else:

mercurial/utils/procutil.py

@@ -281,7 +281,7 b' def hgexecutable():'
         if hg:
             _sethgexecutable(hg)
         elif mainfrozen():
-            if getattr(sys, 'frozen', None) == b'macosx_app':
+            if getattr(sys, 'frozen', None) == 'macosx_app':
                 # Env variable set by py2app
                 _sethgexecutable(encoding.environ[b'EXECUTABLEPATH'])
             else:
@@ -457,7 +457,7 b' def hgcmd():'
     get either the python call or current executable.
     """
     if mainfrozen():
-        if getattr(sys, 'frozen', None) == b'macosx_app':
+        if getattr(sys, 'frozen', None) == 'macosx_app':
             # Env variable set by py2app
             return [encoding.environ[b'EXECUTABLEPATH']]
         else: