Extract function `read_password_stdin`

This ensures that `wallet_utils.py` and `genwallet.py` use the same logic for
reading the password.

The current algorithm for reading the password entails some
non-obvious details like utf-8 encoding and not stripping trailing
newlines.

jmclient/jmclient/wallet_utils.py

@@ -1368,8 +1368,7 @@ def open_test_wallet_maybe(path, seed, max_mixdepth,
             return test_wallet_cls(storage, **kwargs)
 
     if wallet_password_stdin is True:
-        stdin = sys.stdin.read()
+        password = read_password_stdin()
-        password = stdin.encode('utf-8')
         return open_wallet(path, ask_for_password=False, password=password, mixdepth=max_mixdepth, **kwargs)
 
     return open_wallet(path, mixdepth=max_mixdepth, **kwargs)
@@ -1444,6 +1443,10 @@ def get_wallet_path(file_name, wallet_dir=None):
     return os.path.join(wallet_dir, file_name)
 
 
+def read_password_stdin():
+    return sys.stdin.read().encode('utf-8')
+
+
 def wallet_tool_main(wallet_root_path):
     """Main wallet tool script function; returned is a string (output or error)
     """

scripts/genwallet.py

@@ -3,7 +3,6 @@
 # A script for noninteractively creating wallets.
 # The implementation is similar to wallet_generate_recover_bip39 in jmclient/wallet_utils.py
 
-import sys
 import os
 from optparse import OptionParser
 from jmclient import (
@@ -23,7 +22,7 @@ def main():
     (options, args) = parser.parse_args()
     wallet_name = args[0]
     if options.wallet_password_stdin:
-        password = sys.stdin.read().encode("utf-8")
+        password = wallet_utils.read_password_stdin()
     else:
         assert len(args) > 1, "must provide password via stdin (see --help), or as second argument."
         password = args[1].encode("utf-8")