init v3.3.9
catch specific HTTPErrors
update data ranges
add badge sourcegraph
return data if parser is None
pragma
put names in named parameters
clean white space
change 'exists' to a more general condition
consistent use of os.path. isdir, isfile and exists
add CONTRIBUTING guidelines
add pep8 and pep257 links
typo
fmt
add link to code 'discussion'
fmt
add log warning when isbn is not valid and return None
invalidate ISBN-13 of series not yet allocated (not 978... 979...)
add more tests to mask
set complexity to 11