Add utilities to extract from rpm and from deb

[willianrampazzo]

On QEMU tests/acceptance/boot_linux_console.py, the LinuxKernelTest class has two utility methods to extract from deb and from rpm. It would be good if we could add those two utilities to our avocado/utils.

Code from QEMU:

    def extract_from_deb(self, deb, path):
        """
        Extracts a file from a deb package into the test workdir

        :param deb: path to the deb archive
        :param path: path within the deb archive of the file to be extracted
        :returns: path of the extracted file
        """
        cwd = os.getcwd()
        os.chdir(self.workdir)
        file_path = process.run("ar t %s" % deb).stdout_text.split()[2]
        process.run("ar x %s %s" % (deb, file_path))
        archive.extract(file_path, self.workdir)
        os.chdir(cwd)
        # Return complete path to extracted file.  Because callers to
        # extract_from_deb() specify 'path' with a leading slash, it is
        # necessary to use os.path.relpath() as otherwise os.path.join()
        # interprets it as an absolute path and drops the self.workdir part.
        return os.path.normpath(os.path.join(self.workdir,
                                             os.path.relpath(path, '/')))

    def extract_from_rpm(self, rpm, path):
        """
        Extracts a file from an RPM package into the test workdir.

        :param rpm: path to the rpm archive
        :param path: path within the rpm archive of the file to be extracted
                     needs to be a relative path (starting with './') because
                     cpio(1), which is used to extract the file, expects that.
        :returns: path of the extracted file
        """
        cwd = os.getcwd()
        os.chdir(self.workdir)
        process.run("rpm2cpio %s | cpio -id %s" % (rpm, path), shell=True)
        os.chdir(cwd)
        return os.path.normpath(os.path.join(self.workdir, path))

[beraldoleal]

@willianrampazzo is this a duplicate from #3549 ? If so, let's close this.

I'm already investigating this there.

[willianrampazzo]

Closing as a duplicate from #3549.