building in dedicated build-tree broken
The fix for #5126 (closed) breaks building in dedicated build-trees:
../build-tree$ make
make all-am
make[1]: Entering directory `/home/weasel/projects/debian/debian/obfsproxy/obfsproxy/build-tree'
/bin/sed -e 's,[@]PYTHON[@],/usr/bin/python,' < src/test/tester.py.in > tester.py
/bin/bash: src/test/tester.py.in: No such file or directory
make[1]: *** [tester.py] Error 1
make[1]: Leaving directory `/home/weasel/projects/debian/debian/obfsproxy/obfsproxy/build-tree'
make: *** [all] Error 2