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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_venvs(self):
 """Returns a list of names of available virtual environments. :raises: DjangoDevException on errors :rtype: list :return: list of names """


        def raise_():
            error_str = 'Virtual environments are not created. Please run `bootstrap` command.'
            self.logger.error(error_str)
            raise DjangoDevException(error_str)

        if not os.path.exists(self.venvs_path):
            raise_()
        venvs = os.listdir(self.venvs_path)
        if not venvs:
            raise_()

        venvs.sort()
        return venvs