Use install(1) to install mnexec so that setup.py develop works.

Makefile

-all: codecheck test
-
-clean:
-	rm -rf build dist *.egg-info *.pyc mnexec bin/mnexec
-
 MININET = mininet/*.py
 TEST = mininet/test/*.py
 EXAMPLES = examples/*.py
 BIN = bin/mn
 PYSRC = $(MININET) $(TEST) $(EXAMPLES) $(BIN)
-
+MNEXEC = mnexec
 P8IGN = E251,E201,E302,E202
 
+all: codecheck test
+
+clean:
+	rm -rf build dist *.egg-info *.pyc $(MNEXEC)
+
 codecheck: $(PYSRC)
 	-echo "Running code check"
 	pyflakes $(PYSRC)
@@ -26,10 +26,14 @@ test: $(MININET) $(TEST)
 	-echo "Running tests"
 	mininet/test/test_nets.py
 
-install: mnexec
-	cp mnexec bin/
+install: $(MNEXEC)
+	install $(MNEXEC) /usr/local/bin/
 	python setup.py install
 
+develop: $(MNEXEC)
+	install $(MNEXEC) /usr/local/bin/
+	python setup.py develop
+
 doc:
 	doxygen doxygen.cfg
 

setup.py

@@ -5,8 +5,7 @@
 from setuptools import setup, find_packages
 from os.path import join
 
-scripts = [ join( 'bin', filename ) for filename in [ 
-    'mn', 'mnexec' ] ]
+scripts = [ join( 'bin', filename ) for filename in [ 'mn' ] ]
 
 modname = distname = 'mininet'