Don't output the whole log for substituting derivations

Just the last bit, as it could be very long.

1 files changed, 9 insertions, 3 deletions

diff --git a/guix-build-coordinator/utils.scm b/guix-build-coordinator/utils.scm
index 1401ac8..69cd743 100644
--- a/guix-build-coordinator/utils.scm
+++ b/guix-build-coordinator/utils.scm
@@ -445,13 +445,19 @@ context."
 
     (with-exception-handler
         (lambda (exn)
-          (let ((log-string
-                 (get-output-string log-port)))
+          (let* ((log-string
+                  (get-output-string log-port))
+                 (lines
+                  (string-split log-string #\newline))
+                 (last-n-lines
+                  (if (< 10 (length lines))
+                      (take-right lines 10)
+                      lines)))
             (close-output-port log-port)
             (simple-format
              (current-error-port)
              "exception when substituting derivation: ~A:\n  ~A\n"
-             exn log-string)
+             exn (string-join last-n-lines "\n"))
             (raise-exception exn)))
       (lambda ()
         (parameterize ((current-build-output-port log-port))