Reduced number of parallel jobs, I suspect this is making the travis-ci build fail.

graph-lib/Makefile

@@ -7,7 +7,7 @@ make/make: make/make.rkt make/lib.rkt
 
 .PHONY: clean
 clean:
-	rm -fr make/make docs coverage
+	rm -fr make/make docs
 	find \( -path ./lib/doc/bracket -prune -and -false \) -or -name compiled -print0 | xargs -0 rm -rf
 
 .PHONY: build-dep

graph-lib/make/lib.rkt

@@ -226,12 +226,12 @@
                                 " "))
         (display "\033[1;34m")
         (flush-output)
-        (let ((result (apply system* arg0 args)))
+        (let ((exit-code (apply system*/exit-code arg0 args)))
           (display "\033[m")
           (flush-output)
-          (unless result
-            (raise "Command failed."))
-          result))))
+          (unless (= exit-code 0)
+            (raise (format "Command failed with exit code ~a." exit-code)))
+          (= exit-code 0)))))
 
 (define-syntax-rule (run! . rest) (let () (run . rest) (values)))
 

graph-lib/make/make.rkt

@@ -137,7 +137,7 @@
 
 (run! `(,(find-executable-path-or-fail "raco")
         "make"
-        "-j" "8"
+        "-j" "5"
         ,@rkt-files))
 
 ;; Create root MathJax link, must be done before the others