Revert "find_sdk_tools_cmd returns non if aapt is not found"

This reverts commit 66414a9fc7.

tests/common.TestCase

@@ -715,9 +715,10 @@ class CommonTest(unittest.TestCase):
         fdroidserver.common.fill_config_defaults(config)
         fdroidserver.common.config = config
         self._set_build_tools()
-        aapt = fdroidserver.common.find_sdk_tools_cmd('aapt')
-        if aapt:
+        try:
             config['aapt'] = fdroidserver.common.find_sdk_tools_cmd('aapt')
+        except fdroidserver.exception.FDroidException:
+            pass  # aapt is not required if androguard is present
 
         testcases = [
             ('repo/obb.main.twoversions_1101613.apk', 'obb.main.twoversions', '1101613', '0.1'),