Update PGP keys during _PostRepoUpgrade in `sync`

Previously, if a key was added, a client wouldn't add the key during
the sync step.  This would cause issues if a new key were added and a
subsequent release were signed by that key.

Change-Id: I4fac317573cd9d0e8da62aa42e00faf08bfeb26c
diff --git a/repo b/repo
index 7942851..5f328a4 100755
--- a/repo
+++ b/repo
@@ -28,7 +28,7 @@
 del magic
 
 # increment this whenever we make important changes to this script
-VERSION = (1, 17)
+VERSION = (1, 18)
 
 # increment this if the MAINTAINER_KEYS block is modified
 KEYRING_VERSION = (1,0)
@@ -80,7 +80,7 @@
 GIT = 'git'                     # our git command
 MIN_GIT_VERSION = (1, 5, 4)     # minimum supported git version
 repodir = '.repo'               # name of repo's private directory
-S_repo = 'repo'                 # special repo reposiory
+S_repo = 'repo'                 # special repo repository
 S_manifests = 'manifests'       # special manifest repository
 REPO_MAIN = S_repo + '/main.py' # main script
 
@@ -130,7 +130,7 @@
                  metavar='GROUP')
 group.add_option('-p', '--platform',
                  dest='platform', default="auto",
-                 help='restrict manifest projects to ones with a specified'
+                 help='restrict manifest projects to ones with a specified '
                       'platform group [auto|all|none|linux|darwin|...]',
                  metavar='PLATFORM')
 
@@ -196,8 +196,8 @@
 
   _CheckGitVersion()
   try:
-    if _NeedSetupGnuPG():
-      can_verify = _SetupGnuPG(opt.quiet)
+    if NeedSetupGnuPG():
+      can_verify = SetupGnuPG(opt.quiet)
     else:
       can_verify = True
 
@@ -246,7 +246,7 @@
     raise CloneFailure()
 
 
-def _NeedSetupGnuPG():
+def NeedSetupGnuPG():
   if not os.path.isdir(home_dot_repo):
     return True
 
@@ -264,7 +264,7 @@
   return False
 
 
-def _SetupGnuPG(quiet):
+def SetupGnuPG(quiet):
   if not os.path.isdir(home_dot_repo):
     try:
       os.mkdir(home_dot_repo)