[master] 5772d3c bail out with a clear error if graphviz is missing for building the html and pdf targets

[Nils Goroll]

commit 5772d3cf7f8f93662c08a778a1c84a4571d442ce
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Mon Oct 13 18:38:56 2014 +0200

    bail out with a clear error if graphviz is missing for building the html and pdf targets

diff --git a/doc/graphviz/Makefile.am b/doc/graphviz/Makefile.am
index dc3c3be..dd2ef4c 100644
--- a/doc/graphviz/Makefile.am
+++ b/doc/graphviz/Makefile.am
@@ -21,7 +21,6 @@ dist-hook:
 SIZE	      = 8.4,11.7
 
 if HAVE_DOT
-
 PDFS = \
 	cache_http1_fsm.pdf \
 	cache_req_fsm.pdf \
@@ -31,11 +30,22 @@ SVGS = \
 	cache_http1_fsm.svg \
 	cache_req_fsm.svg \
 	cache_fetch.svg
+endif
 
 pdf: $(PDFS)
+if ! HAVE_DOT
+	@echo ==================================================
+	@echo You need graphviz installed to generate pdf output
+	@echo ==================================================
+	@false
+endif
 
 html: $(SVGS) link_srcdir
-
+if ! HAVE_DOT
+	@echo ===================================================
+	@echo You need graphviz installed to generate html output
+	@echo ===================================================
+	@false
 endif
 
 # XXX does not fit onto a4 unless in landscape