Add DEBUG; when set to 1 traceback will be shown

example/Makefile

@@ -9,13 +9,17 @@ PAPER         ?=
 BUILDDIR      ?= _build
 
 # logging variables
+DEBUG ?= 0
 LOGLEVEL =? WARNING
 export LOGLEVEL=${LOGLEVEL}
 
 # Internal variables.
 PAPEROPT_a4     = -D latex_paper_size=a4
 PAPEROPT_letter = -D latex_paper_size=letter
-ALLSPHINXOPTS   = -ET -d $(BUILDDIR)/doctrees $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
+ALLSPHINXOPTS   = -E -d $(BUILDDIR)/doctrees $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
+ifeq (${DEBUG}, 1)
+ALLSPHINXOPTS += -T
+endif
 # the i18n builder cannot share the environment and doctrees with the others
 I18NSPHINXOPTS  = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .