(maint) Fix missed header file for CFACT-139 fix

CFACT-139 moved code using the system_error call, but didn't move the
required header file. CI missed it because unity-build ensured the header
was there.
Merge pull request #206 from MikaelSmith/maint/master/fix-missed-system_error-merge

(maint) Fix missed header file for CFACT-139 fix