Fix pylint warning W0108: Lambda may not be necessary

Remove unnecessary usage of lambda.

Change-Id: I06d41933057d60d15d307ee800cca052a44754c6
diff --git a/main.py b/main.py
index 10e1cf8..6236dd3 100755
--- a/main.py
+++ b/main.py
@@ -195,12 +195,12 @@
     sys.exit(1)
 
   exp = _CurrentWrapperVersion()
-  ver = tuple(map(lambda x: int(x), ver.split('.')))
+  ver = tuple(map(int, ver.split('.')))
   if len(ver) == 1:
     ver = (0, ver[0])
 
+  exp_str = '.'.join(map(str, exp))
   if exp[0] > ver[0] or ver < (0, 4):
-    exp_str = '.'.join(map(lambda x: str(x), exp))
     print >>sys.stderr, """
 !!! A new repo command (%5s) is available.    !!!
 !!! You must upgrade before you can continue:   !!!
@@ -210,7 +210,6 @@
     sys.exit(1)
 
   if exp > ver:
-    exp_str = '.'.join(map(lambda x: str(x), exp))
     print >>sys.stderr, """
 ... A new repo command (%5s) is available.
 ... You should upgrade soon:
@@ -272,7 +271,7 @@
     _user_agent = 'git-repo/%s (%s) git/%s Python/%d.%d.%d' % (
       repo_version,
       os_name,
-      '.'.join(map(lambda d: str(d), git.version_tuple())),
+      '.'.join(map(str, git.version_tuple())),
       py_version[0], py_version[1], py_version[2])
   return _user_agent