Initial guess for file encoding (utf8)undefined

```
Initial guess for file encoding (utf8)undefined
(biblatex)                and new guess (UTF-8)	do not match.
(biblatex)	Please set up your document encoding *before*
(biblatex)	loading biblatex.
(biblatex)	The case changing code might not work as expected.
```

这个现象的产生原因是`\documentclass[UTF8]{pkuthss}`和`\usepackage[utf8]{biblatex}`冲突