Fail on Deflate64 compressed files

[idiom]

Return mode=failed with Deflate64 compressed files. These fail with the unzip package and causes a runtime exception to be thrown and processing to stop when running through a directory of files.

A future enhancement could be to detect these types of compressed zip files and use the 7z unpacker instead.

[jbremer]

You make a good point. In fact, perhaps it would be a good step forward to have .7z take precedence over .zip unpacking, so that any .zip file is unpacked with .7z, if available. This would also make sense performance-wise etc.

[coveralls]

Coverage increased (+0.03%) to 92.837% when pulling a3b950d on idiom:pull_requests into 31c28ab on jbremer:master.

[codecov-io]

Codecov Report

Merging #10 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #10      +/-   ##
==========================================
+ Coverage   93.51%   93.53%   +0.02%     
==========================================
  Files          18       18              
  Lines         709      712       +3     
==========================================
+ Hits          663      666       +3     
  Misses         46       46

Impacted Files	Coverage Δ
sflock/unpack/zip.py	95.74% <100%> (+0.29%)	✅

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[idiom]

Hmm this fell off my radar =\ I'll close this pull request and take a look at the associated issue.