Move signer decision into import tree

Author: fahhem

adb/adb_debug.py

@@ -27,12 +27,13 @@
 
 try:
   import sign_m2crypto
+  rsa_signer = sign_m2crypto.M2CryptoSigner
 except ImportError:
-  sign_m2crypto = None
-try:
-  import sign_pythonrsa
-except ImportError:
-  sign_pythonrsa = None
+  try:
+    import sign_pythonrsa
+    rsa_signer = sign_pythonrsa.PythonRSASigner.FromRSAKeyPath
+  except ImportError:
+    rsa_signer = None
 
 
 gflags.ADOPT_module_key_flags(common_cli)
@@ -47,14 +48,11 @@
 
 def GetRSAKwargs():
   if FLAGS.rsa_key_path:
-    if not sign_m2crypto and not sign_pythonrsa:
+    if rsa_signer is None:
       print >> sys.stderr, 'Please install either M2Crypto or python-rsa'
       sys.exit(1)
-    signer = (
-        sign_m2crypto.M2CryptoSigner if sign_m2crypto
-        else sign_pythonrsa.PythonRSASigner.FromRSAKeyPath)
     return {
-        'rsa_keys': [signer(os.path.expanduser(path))
+        'rsa_keys': [rsa_signer(os.path.expanduser(path))
                      for path in FLAGS.rsa_key_path],
         'auth_timeout_ms': int(FLAGS.auth_timeout_s * 1000.0),
     }