reviewed py3 compat in pipelines/images.py and pipelines/files.py

Author: lopuhin

tests/py3-ignores.txt

@@ -11,8 +11,6 @@ scrapy/xlib/tx/_newclient.py
 scrapy/xlib/tx/__init__.py
 scrapy/core/downloader/handlers/s3.py
 scrapy/core/downloader/handlers/ftp.py
-scrapy/pipelines/images.py
-scrapy/pipelines/files.py
 scrapy/linkextractors/sgml.py
 scrapy/linkextractors/regex.py
 scrapy/linkextractors/htmlparser.py