dgit build: Better message when network is offline.

When build fails because the archive access fails, mention that this
was tried because --since-version was not specified.

Closes:#883340.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

1 files changed, 15 insertions, 7 deletions

diff --git a/dgit b/dgit
index 2cf78ec..9084eaf 100755
--- a/dgit
+++ b/dgit
@@ -6018,13 +6018,21 @@ sub changesopts_initial () {
 
 sub changesopts_version () {
     if (!defined $changes_since_version) {
-	my @vsns = archive_query('archive_query');
-	my @quirk = access_quirk();
-	if ($quirk[0] eq 'backports') {
-	    local $isuite = $quirk[2];
-	    local $csuite;
-	    canonicalise_suite();
-	    push @vsns, archive_query('archive_query');
+	my @vsns;
+	unless (eval {
+	    @vsns = archive_query('archive_query');
+	    my @quirk = access_quirk();
+	    if ($quirk[0] eq 'backports') {
+		local $isuite = $quirk[2];
+		local $csuite;
+		canonicalise_suite();
+		push @vsns, archive_query('archive_query');
+	    }
+	    1;
+	}) {
+	    print STDERR $@;
+	    fail
+ "archive query failed (queried because --since-version not specified)";
 	}
 	if (@vsns) {
 	    @vsns = map { $_->[0] } @vsns;