pcre2el is not loaded in spacemacs-base, but needed for ivy-ag support.

layers/+completion/spacemacs-ivy/packages.el

@@ -17,6 +17,7 @@
         ;; treat it as a stand-alone package
         (ivy :location built-in)
         (ivy-spacemacs-help :location local)
+        pcre2el
         smex
         swiper
         wgrep))
@@ -514,6 +515,9 @@ perspectives does."
               ("C" spacemacs/ivy-persp-close-other :exit t)
               ("X" spacemacs/ivy-persp-kill-other :exit t))))))
 
+(defun spacemacs-ivy/init-pcre2el ()
+  (use-package pcre2el :defer t))
+
 (defun spacemacs-ivy/init-smex ()
   (use-package smex
     :defer t