前言：同學們在用pip install的時候，可能會遇到MemoryError的問題
報錯如下，看最后一行的memory error關鍵字：
報錯的原因大致如下：（詳細細節可以查看此處）
**This error is coming up because, it seems, pip's caching mechanism is trying to read the entire file into memory before caching it… which poses a problem in a limited-memory environment, as matplotlib is ~50mb.
** 解決辦法：加個參數即可：
pip --no-cache-dir install pyspark
