Here is the output of powershell:
PS C:\Python27> python pywallet.py --dumpwallet --datadir=. > wallet.txt
pywallet.py:22: UserWarning: Python 3 support is still experimental, you may encounter bugs
WARNING:root:pycrypto or libssl not found, decryption may be slow
PS C:\Python27>
The wallet.txt data contains:
'ecdsa' package is not installed, pywallet won't be able to sign/verify messages
Depreacation
The --datadir option has been deprecated, now the full path of the wallet file should go to --wallet
If you're not sure what to do, concatenating the old --datadir content, then a directory separator, then the old --wallet should do the trick
If not, ask for help in the Pywallet thread:
https://bitcointalk.org/index.php?topic=34028A mandatory option is missing
Usage: pywallet.py [options]
Options:

(((
PyWallet is in the process of being updated by the author who has made some "breaking" changes... and unfortunately, a lot of the old "tutorials" and commands no longer work.
So, do as the deprecation message suggested and use the --wallet option instead of --datadir:
This assumes that your "wallet.dat" file is actually called wallet.dat and is in the same directory as the pywallet.py script file... if not, just change wallet.dat to be the full path to the "wallet.dat" file