Description of problem:
When user tries to use following command, it raises TypeError

# echo -e "Secret123\nSecret123\nSecret123\n" | ipa vault-add PrivateVault2
--desc="Private vault2"
New password:
ipa: ERROR: non-public: TypeError: decode() argument 1 must be string, not None
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ipalib/backend.py", line 139, in
execute
    result = self.Command[_name](*args, **options)
  File "/usr/lib/python2.7/site-packages/ipalib/frontend.py", line 447, in
__call__
    return self.__do_call(*args, **options)
  File "/usr/lib/python2.7/site-packages/ipalib/frontend.py", line 475, in
__do_call
    ret = self.run(*args, **options)
  File "/usr/lib/python2.7/site-packages/ipalib/frontend.py", line 1199, in run
    return self.forward(*args, **options)
  File "/usr/lib/python2.7/site-packages/ipaclient/plugins/vault.py", line 307,
in forward
    password = get_new_password()
  File "/usr/lib/python2.7/site-packages/ipaclient/plugins/vault.py", line 93,
in get_new_password
    sys.stdin.encoding)
TypeError: decode() argument 1 must be string, not None
ipa: ERROR: an internal error has occurred


Version-Release number of selected component (if applicable):
# rpm -q freeipa-server freeipa-client ipa-server ipa-client 389-ds-base pki-ca
krb5-server
package freeipa-server is not installed
package freeipa-client is not installed
ipa-server-4.5.0-8.el7.x86_64
ipa-client-4.5.0-8.el7.x86_64
389-ds-base-1.3.6.1-9.el7.x86_64
pki-ca-10.4.1-2.el7.noarch
krb5-server-1.15.1-7.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. echo -e "Secret123\nSecret123\nSecret123\n" | ipa vault-add PrivateVault2
--desc="Private vault2"
2. Press enter on "New Password:" prompt

Actual results:
Error above mentioned.

Expected results:
Error should be replaced with appropriate warning message.