dispatch_io unit test: Gracefully handle permission failures
dispatch_io unit test: Gracefully handle permission failures

PSPDFKit-labs/libdispatch,SproutOrc/libdispatch,nickhutchinson/libdispatch,PSPDFKit-labs/libdispatch,SproutOrc/libdispatch,PSPDFKit-labs/libdispatch,evaautomation/libdispatch,evaautomation/libdispatch,nickhutchinson/libdispatch,SproutOrc/libdispatch,evaautomation/libdispatch,SproutOrc/libdispatch,PSPDFKit-labs/libdispatch,evaautomation/libdispatch,nickhutchinson/libdispatch,nickhutchinson/libdispatch