import-checker.py: exit with code 0 if no error is detected

Before this patch, `import-checker.py` exits with non-0 code, if no
error is detected. This is unusual as Unix command.

This change may be a one of preparations for issue4677, because this
can avoid extra explanation about unusual exit code of
`import-checker.py` for third party tool developers.

contrib/import-checker.py

@@ -564,7 +564,7 b' def main(argv):'
             print 'Import cycle:', c
             firstmods.add(first)
         any_errors = True
-    return not any_errors
+    return any_errors != 0
 
 if __name__ == '__main__':
     sys.exit(int(main(sys.argv)))

tests/test-module-imports.t

@@ -101,6 +101,7 b' Run additional tests for the import chec'
   testpackage/subpackage/levelpriority.py higher-level import should come first: testpackage
   testpackage/symbolimport.py direct symbol import from testpackage.unsorted
   testpackage/unsorted.py imports not lexically sorted: os < sys
+  [1]
 
   $ cd "$TESTDIR"/..
 
@@ -129,3 +130,4 b' these may expose other cycles.'
   Import cycle: mercurial.cmdutil -> mercurial.context -> mercurial.subrepo -> mercurial.cmdutil
   Import cycle: hgext.largefiles.basestore -> hgext.largefiles.localstore -> hgext.largefiles.basestore
   Import cycle: mercurial.commands -> mercurial.commandserver -> mercurial.dispatch -> mercurial.commands
+  [1]