Bug 1275437 - Fixed some offending version checks that were inhereted from the BaseBootstrapper r=gps

Overrode BaseBootstrapper.which to append '.exe' to any which checks since (hopefully) anything the bootstrapper looks for, must be a windows executable.

Changed base bootstrapper class to use str instead of unicode to avoid a bug in the MinGW version of Python where subprocces.Popen will not accept environment variables that are in unicode instead of str.

MozReview-Commit-ID: 4m8xNifawYS

--HG--
extra : rebase_source : 455b518b099fdba347626ab93b85ddbd44f1f977

python/mozboot/mozboot/base.py

@@ -299,7 +299,8 @@ class BaseBootstrapper(object):
         making it suitable for use in scripts.
         """
         env = os.environ.copy()
-        env['HGPLAIN'] = '1'
+        env[b'HGPLAIN'] = b'1'
+
         return env
 
     def is_mercurial_modern(self):

python/mozboot/mozboot/windows.py

@@ -42,11 +42,14 @@ class WindowsBootstrapper(BaseBootstrapper):
                                       'to set up a build environment on Windows. If you are testing Windows Bootstrap support, '
                                       'try `export MOZ_WINDOWS_BOOTSTRAP=1`')
         BaseBootstrapper.__init__(self, **kwargs)
-        if not self.which('pacman.exe'):
+        if not self.which('pacman'):
             raise NotImplementedError('The Windows bootstrapper only works with msys2 with pacman. Get msys2 at '
                                       'http://msys2.github.io/')
         print 'Using an experimental bootstrapper for Windows.'
 
+    def which(self, name):
+        return BaseBootstrapper.which(self, name + '.exe')
+
     def install_system_packages(self):
         self.pacman_install(*self.SYSTEM_PACKAGES)