Encode the environment variables passed to git

Windows allows the environment to have unicode values.
This will cause Python to fail to execute the command.

Change-Id: I37d922c3d7ced0d5b4883f0220346ac42defc5e9
Signed-off-by: Shawn O. Pearce <sop@google.com>

subcmds/forall.py

@@ -151,11 +151,11 @@ terminal and are not redirected.
     first = True
 
     for project in self.GetProjects(args):
-      env = dict(os.environ.iteritems())
+      env = os.environ.copy()
       def setenv(name, val):
         if val is None:
           val = ''
-        env[name] = val
+        env[name] = val.encode()
 
       setenv('REPO_PROJECT', project.name)
       setenv('REPO_PATH', project.relpath)

subcmds/sync.py

@@ -269,7 +269,7 @@ uncommitted changes are present' % project.relpath
         if branch.startswith(R_HEADS):
           branch = branch[len(R_HEADS):]
 
-        env = dict(os.environ)
+        env = os.environ.copy()
         if (env.has_key('TARGET_PRODUCT') and
             env.has_key('TARGET_BUILD_VARIANT')):
           target = '%s-%s' % (env['TARGET_PRODUCT'],
@@ -413,9 +413,9 @@ warning: Cannot automatically authenticate repo."""
       % (project.name, rev)
     return False
 
-  env = dict(os.environ)
-  env['GIT_DIR'] = project.gitdir
-  env['GNUPGHOME'] = gpg_dir
+  env = os.environ.copy()
+  env['GIT_DIR'] = project.gitdir.encode()
+  env['GNUPGHOME'] = gpg_dir.encode()
 
   cmd = [GIT, 'tag', '-v', cur]
   proc = subprocess.Popen(cmd,