code: def from_env(cls, hashbang):
      
      paths = os.getenv('PATH', '').split(':')
      for path in paths:
        for fn in cls.expand_path(path):
          basefile = os.path.basename(fn)
          if hashbang == basefile:
            try:
              return cls.from_binary(fn)
            except Exception as e:
              TRACER.log('Could not identify %s: %s' % (fn, e))
docs: Resolve a PythonInterpreter as /usr/bin/env would.
  
         :param hashbang: A string, e.g. "python3.3" representing some binary on the $PATH.