The build system installs stray pyc files.

--- a/python3/Makefile.am
+++ b/python3/Makefile.am
@@ -40,9 +40,7 @@
 
 # Install as _DATA rather than _SCRIPTS because we don't want to make these
 # executable (they don't have a #! line).
-pkgpylib_DATA = xapian/__init__.py \
-		xapian/__pycache__/__init__.@PYTHON3_CACHE_TAG@.pyc \
-		xapian/__pycache__/__init__.@PYTHON3_CACHE_OPT1_EXT@
+pkgpylib_DATA = xapian/__init__.py
 
 pkgpylib_LTLIBRARIES = _xapian.la