Only install auctex if xelatex is found.

init.el

@@ -1,5 +1,5 @@
 ;;; init.el --- tastytea's Emacs init file.
-;;; Time-stamp: <2019-04-02 15:16:18 CEST>
+;;; Time-stamp: <2019-04-03 14:21:51 CEST>
 
 ;;; Commentary:
 ;;; I am using this file with Emacs 26, but most of it will probably work with
@@ -676,24 +676,24 @@
   (find-file . auto-insert))
 
 ;;;;;;;;;;;;;;;;;;;; LaTeX ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-(use-package tex-site
-  :if (executable-find "xelatex")
-  :ensure auctex
-  :custom
-  (TeX-parse-self t)               ; Enable parse on load.
-  (TeX-auto-save t)                ; Enable parse on save
-  (TeX-PDF-mode t)                 ; PDF mode (rather than DVI-mode)
-  (TeX-engine 'xelatex)
-  ;; To use pdf-tools with auctex.
-  ;; https://emacs.stackexchange.com/a/21764/21935
-  (TeX-view-program-selection '((output-pdf "PDF Tools")))
-  (TeX-view-program-list '(("PDF Tools" TeX-pdf-tools-sync-view)))
-  :mode
-  ("\\.tex\\'" . LaTeX-mode)
-  :config
-  ;; To have the buffer refresh after compilation.
-  (add-hook 'TeX-after-compilation-finished-functions
-            #'TeX-revert-document-buffer))
+(if (executable-find "xelatex")
+    (use-package tex-site
+      :ensure auctex
+      :custom
+      (TeX-parse-self t)               ; Enable parse on load.
+      (TeX-auto-save t)                ; Enable parse on save
+      (TeX-PDF-mode t)                 ; PDF mode (rather than DVI-mode)
+      (TeX-engine 'xelatex)
+      ;; To use pdf-tools with auctex.
+      ;; https://emacs.stackexchange.com/a/21764/21935
+      (TeX-view-program-selection '((output-pdf "PDF Tools")))
+      (TeX-view-program-list '(("PDF Tools" TeX-pdf-tools-sync-view)))
+      :mode
+      ("\\.tex\\'" . LaTeX-mode)
+      :config
+      ;; To have the buffer refresh after compilation.
+      (add-hook 'TeX-after-compilation-finished-functions
+                #'TeX-revert-document-buffer)))
 
 ;; Auto complete for LaTeX.
 (use-package company-auctex