title: RuntimeError: Cannot determine web2py version
body: <p>I download and installed web2py 2.5.1 stable on my system, and reading the book I tried to start the application by running <code>w2p_run</code> but I got this exception:</p>
  
  <pre><code>jorge [~] ~&gt; w2p_run 
  WARNING:root:Unable to import plural rules: No module named plural_rules
  Traceback (most recent call last):
    File "/usr/bin/w2p_run", line 5, in &lt;module&gt;
      pkg_resources.run_script('web2py==2.5.1-stable-timestamp.2013.06.06.15.39.19', 'w2p_run')
    File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 505, in run_script
      self.require(requires)[0].run_script(script_name, ns)
    File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 1245, in run_script
      execfile(script_filename, namespace, namespace)
    File "/usr/lib/python2.7/site-packages/web2py-2.5.1_stable_timestamp.2013.06.06.15.39.19-py2.7.egg/EGG-INFO/scripts/w2p_run", line 17, in &lt;module&gt;
      import gluon.widget
    File "/usr/lib/python2.7/site-packages/web2py-2.5.1_stable_timestamp.2013.06.06.15.39.19-py2.7.egg/gluon/widget.py", line 25, in &lt;module&gt;
      import main
    File "/usr/lib/python2.7/site-packages/web2py-2.5.1_stable_timestamp.2013.06.06.15.39.19-py2.7.egg/gluon/main.py", line 120, in &lt;module&gt;
      raise RuntimeError("Cannot determine web2py version")
  RuntimeError: Cannot determine web2py version
  jorge [~] ~&gt; 
  </code></pre>
  
  <p>I really wants to start using web2py, so, Any help? :(</p>