python: replace hardcoding of SONAME version

Failing to update this string in globals.py causes failures when the
SONAME changes.  In order to hopefully reduce the number of such
errors, automate the process of setting the SONAME in the python
bindings.

Makefile.local

@@ -107,7 +107,9 @@ dist: $(TAR_FILE)
 .PHONY: update-versions
 
 update-versions:
-	sed -i "s/^__VERSION__[[:blank:]]*=.*$$/__VERSION__ = \'${VERSION}\'/" $(PV_FILE)
+	sed -i -e "s/^__VERSION__[[:blank:]]*=.*$$/__VERSION__ = \'${VERSION}\'/" \
+	    -e "s/^SOVERSION[[:blank:]]*=.*$$/SOVERSION = \'${LIBNOTMUCH_VERSION_MAJOR}\'/" \
+	    ${PV_FILE}
 
 # We invoke make recursively only to force ordering of our phony
 # targets in the case of parallel invocation of make (-j).

bindings/python/notmuch/globals.py

@@ -18,15 +18,16 @@ Copyright 2010 Sebastian Spaeth <Sebastian@SSpaeth.de>
 """
 
 from ctypes import CDLL, Structure, POINTER
+from version import SOVERSION
 
 #-----------------------------------------------------------------------------
 #package-global instance of the notmuch library
 try:
     from os import uname
     if uname()[0] == 'Darwin':
-        nmlib = CDLL("libnotmuch.4.dylib")
+        nmlib = CDLL("libnotmuch.{0:s}.dylib".format(SOVERSION))
     else:
-        nmlib = CDLL("libnotmuch.so.4")
+        nmlib = CDLL("libnotmuch.so.{0:s}".format(SOVERSION))
 except:
     raise ImportError("Could not find shared 'notmuch' library.")
 

bindings/python/notmuch/version.py

@@ -1,2 +1,3 @@
 # this file should be kept in sync with ../../../version
 __VERSION__ = '0.19'
+SOVERSION = '4'