DCOM-137: [GH-218] hotfix cache

[doctrinebot]

Jira issue originally created by user @beberlei:

This issue is created automatically through a Github pull request on behalf of jakoch:

Url: #218

Message:

a) replaced silence operator by is_file() check.
If there is a lock or permission problem while unlinking a file, the error should pop up.
b) replaced little typo in constant name (availiable => available)

[doctrinebot]

Comment created by @beberlei:

A related Github Pull-Request [GH-218] was closed
#218

[doctrinebot]

Comment created by @Ocramius:

Moved to DCOM-138 and DCOM-139

[doctrinebot]

Issue was closed with resolution "Duplicate"