Package not installed if build script not found, but remnants confuse PackageManager

[james-d-mitchell]

I just tried to recreate #95 locally and I get the following where I try to install io-4.7.2 this seems to fail (although this isn't explicitly mentioned below), but then when I try to update io again, I'm told that version 4.7.2 is already installed (which it isn't). Just for the record, when I restart GAP, IO version 4.7.1 is loaded and not 4.7.2.

gap> UpdatePackage("io");
#I  Command wget not found
#I  Retrieving PackageInfo.g from https://gap-packages.github.io/io/PackageInfo.g ...
#I  Command wget not found
#I  io version 4.7.2 will be installed, replacing 4.7.1
#I  Downloading archive from URL https://github.com/gap-packages/io/releases/download/v4.7.2/io-4.7.2.tar.gz ...
#I  Command wget not found
#I  Saved archive to /var/folders/r5/j7m8hftj25q1j17cb8v8k9mr0000gn/T//gaptempdirFwhXgG/io-4.7.2.tar.gz.pkgman
#I  Extracting to /Users/jdm/.gap/pkg/io-4.7.2 ...
#I  Compilation script not found
#I  It should be at /Users/jdm/gap/bin/BuildPackages.sh
Remove old version of io at /Users/jdm/.gap/pkg/io-4.7.1 ? [y/N] n
true
gap> UpdatePackage("io");
#I  Command wget not found
#I  Retrieving PackageInfo.g from https://gap-packages.github.io/io/PackageInfo.g ...
#I  Command wget not found
#I  The newest version of package "io" is already installed
#I  Compilation script not found
#I  It should be at /Users/jdm/gap/bin/BuildPackages.sh
true
gap>