test: import relative to __init__.py

Might fix tests for Debian builders somehow maybe?

test/__init__.py

@@ -2,5 +2,4 @@
 import sys
 import os
 import os.path
-sys.path.insert(0, os.getcwd())
-sys.path.insert(0, os.path.join(os.getcwd(), os.pardir))
+sys.path.insert(0, os.path.join(os.path.split(__file__)[0], '..'))