* method to detect spider creation in crawler
* correct method name
* method to know if crawlers has spiders
* we do not need to issue requests
* set exit code accordingly to spiders in crawlers
* more portable way to check ofr exceptions
* more clear way
* test cases for several spiders per crawler
* grammatically correct name for method
* method is private
* grammatically correct name for method
* method is private
* remove unused import
* correct order of imports
* changes mechanism of obtaining spider status from method to object member
* rename tests
A new root logger is installed when a crawler is created
if one was already installed before.
This allows to respect custom settings related to logging,
such as LOG_LEVEL, LOG_FILE, etc.