for a specific reason I need to install nltk 2.09b in python 2.7 version. But whenever I execute the following command, 

```
pip2 install nltk==2.0b9

```

I get the following error: 

```
Collecting nltk==2.0b9
  Using cached https://files.pythonhosted.org/packages/ea/b3/4c5157bf034437905fbbd3c80e58c8b4a22cf3400db0bdf19dae3079a732/nltk-2.0b9.tar.gz
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    IOError: [Errno 2] No such file or directory: '/private/var/folders/3b/yskb8jks10lf_pqvv1sy7v740000gn/T/pip-install-63jdDZ/nltk/setup.py'

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/3b/yskb8jks10lf_pqvv1sy7v740000gn/T/pip-install-63jdDZ/nltk/

```

But if I run without any version specification I don't get an error. like the following: 

```
pip2 install nltk;

```

How can I solve this issue?