-mkpasswd: fetch password via getpass instead of requiring command line entry

This gives better security, since running programs and their command lines are visible in 'ps'.

pylink-mkpasswd

@@ -4,14 +4,23 @@ Password hashing utility for PyLink IRC Services.
 """
 
 from pylinkirc.coremods.login import pwd_context
+import getpass
 
 if __name__ == '__main__':
     import argparse
 
     parser = argparse.ArgumentParser(description='Hashes a password for use with PyLink IRC Services.')
-    parser.add_argument('password', help='specifies the password to hash')
+    parser.add_argument('password', help='specifies the password to hash', nargs='?', default='')
     args = parser.parse_args()
 
     assert pwd_context, 'Cannot hash passwords because passlib is missing! Install it via "pip3 install passlib".'
-    assert args.password, "Password cannot be empty!"
-    print(pwd_context.encrypt(args.password))
+
+    password = args.password
+
+    # If no password was given, enter one on the command line
+    if not password:
+        password = getpass.getpass()
+
+    password = password.strip()
+    assert password, "Password cannot be empty!"
+    print(pwd_context.encrypt(password))