http.manage: Ask passphrase twice during --export-ca.

caucase/http.py

@@ -1142,9 +1142,16 @@ def manage(argv=None, stdout=sys.stdout):
       file=stdout,
     )
   if args.export_ca is not None:
-    encryption_algorithm = serialization.BestAvailableEncryption(
-      getBytePass('CA export passphrase: ')
+    while True:
+      passphrase = getBytePass(
+        'CA export passphrase: ',
       )
+      if getBytePass(
+        '             (again): ',
+      ) == passphrase:
+        break
+      print('Error: Input does not match, retrying')
+    encryption_algorithm = serialization.BestAvailableEncryption(passphrase)
     with open(args.export_ca, 'wb') as export_ca_file:
       write = export_ca_file.write
       for key_pair in SQLite3Storage(