Fine-tune error reporting of vercode mismatch

I had a recipe that used 'Build Version: 0.1,2,...' with a ' ' between
the : and the version number. This failed in uncomprehensible ways
untill I figured the above out.

Perhaps a better solution would be to make the parser insensitive to
spaces between the ':' and what's after it?

fdroidserver/build.py

@@ -240,9 +240,9 @@ def build_local(app, thisbuild, vcs, build_dir, output_dir, extlib_dir, tmp_dir,
 
     if (version != thisbuild['version'] or
             vercode != thisbuild['vercode']):
-        raise BuildException(("Unexpected version/version code in output"
-                             "APK: %s / %s"
-                             "Expected: %s / %s")
+        raise BuildException(("Unexpected version/version code in output;"
+                             " APK: '%s' / '%s'"
+                             " Expected: '%s' / '%s'")
                              % (version, str(vercode), thisbuild['version'], str(thisbuild['vercode']))
                             )