sub getBuildLog {
    my ($drvPath) = @_;
    my $logPath = "/nix/var/log/nix/drvs/" . basename $drvPath;
    return -e $logPath ? $logPath : undef;
}

        # Check whether a dependency of this build has previously
        # failed.  If so, don't even bother to build, since it will
        # fail anyway.  !!! Once Nix has negative caching, this code
        # can go.
        my @drvDeps = split '\n', `nix-store --query --requisites --include-outputs $drvPath`;
        die "cannot query dependencies of `$drvPath': $?" if $? != 0;
        @drvDeps = grep { $_ =~ /.drv$/ } @drvDeps;
        my @drvOutputs = split '\n', `nix-store --query --outputs @drvDeps`;
        die "cannot query outputs of the dependencies of `$drvPath': $?" if $? != 0;
        foreach my $dep (@drvOutputs) {
            # !!! This checks more than it has to, namely
            # build-time-only dependencies of dependencies (which
            # don't need to be built).  However, it shouldn't matter:
            # if the dependency was built, then presumably *its*
            # dependencies were built as well.
            # !!! should disregard fixed-output derivations (?)
            if (!isValidPath($dep)) {
                my ($step) = $db->resultset('BuildSteps')->search(
                    {outPath => $dep}, {rows => 1, order_by => "stopTime DESC", type => 0, busy => 0});
                if ($step && $step->status != 0) {
                    $buildStatus = 5;
                    $failedDepBuild = $step->build->id;
                    $failedDepStepNr = $step->stepnr;
                    goto done;
                }
            }
        }
        

                my $errorMsg = $4;
                $errorMsg = "build failed previously (cached)" if $3 eq "cached";

                        $step->update({busy => 0, status => 1, errormsg => $4, stoptime => time});

                        $step->update({busy => 0, status => 1, errormsg => $errorMsg, stoptime => time});

                            { stepnr => $buildStepNr++

                            { stepnr => ($buildSteps{$drvPathStep} = $buildStepNr++)

                            , logfile => $4

                            , logfile => getBuildLog($drvPathStep)

                            , errormsg => $4

                            , errormsg => $errorMsg

        my $logPath = "/nix/var/log/nix/drvs/" . basename $drvPath;
        $logPath = undef unless -e $logPath;

            , logfile => $logPath

            , logfile => getBuildLog $drvPath