fix variable initialization in the build integration tests

Summary:
public
The variable could be unitialized when the line number of an error is not in the base JSON report, which is currently the case for the errors in the test cases.

Reviewed By: jvillard

Differential Revision: D2913991

fb-gh-sync-id: d7e3857
shipit-source-id: d7e3857

scripts/build_integration_tests.py

@@ -45,6 +45,7 @@ def quote(s):
 
 
 def string_of_error(e):
+    line = ''
     if issues.JSON_INDEX_LINE in e:
         line = ' on line %s ' % e[issues.JSON_INDEX_LINE]
     msg = '%s in file %s, procedure %s%s' % (