Add TESTFLAGS variable to Makefile to make running nosetests easier.

Change-Id: I7d94577883ad0805281bcac0003df964bfd05cdc

Makefile

@@ -2,6 +2,7 @@ PYTHON = python
 SETUP = $(PYTHON) setup.py
 PYDOCTOR ?= pydoctor
 TESTRUNNER = $(shell which nosetests)
+TESTFLAGS =
 
 all: build
 
@@ -19,13 +20,13 @@ install::
 
 check:: build
 	PYTHONPATH=. $(PYTHON) $(TESTRUNNER) dulwich
-	which git > /dev/null && PYTHONPATH=. $(PYTHON) $(TESTRUNNER) -i compat
+	which git > /dev/null && PYTHONPATH=. $(PYTHON) $(TESTRUNNER) $(TESTFLAGS) -i compat
 
 check-noextensions:: clean
-	PYTHONPATH=. $(PYTHON) $(TESTRUNNER) dulwich
+	PYTHONPATH=. $(PYTHON) $(TESTRUNNER) $(TESTFLAGS) dulwich
 
 check-compat:: build
-	PYTHONPATH=. $(PYTHON) $(TESTRUNNER) -i compat
+	PYTHONPATH=. $(PYTHON) $(TESTRUNNER) $(TESTFLAGS) -i compat
 
 clean::
 	$(SETUP) clean --all