Merge pull request #1761 from wojiushixiaobai/docs

[Update]更新文档

docs/setup_by_ubuntu.rst

@@ -23,7 +23,7 @@
 ::
 
     $ apt-get update && apt-get -y upgrade
-    $ apt-get -y install wget libkrb5-dev libsqlite3-dev gcc make automake libssl-dev zlib1g-dev libmysqlclient-dev libffi-dev git
+    $ apt-get -y install wget libkrb5-dev libsqlite3-dev gcc make automake libssl-dev zlib1g-dev libmysqlclient-dev libffi-dev git xz-utils
 
     # 修改字符集，否则可能报 input/output error的问题，因为日志里打印了中文
     $ apt-get install language-pack-zh-hans