AWS Elasticsearch synonyms using file

I am trying to add synonyms to elastic search as show in this link using a file but it gives me the following error https://www.elastic.co/guide/en/elasticsearch/reference/5.2/analysis-synonym-tokenfilter.html

error":{"root_cause":[{"type":"illegal_argument_exception","reason":"IOException while reading synonyms_path_path: ],"type":"illegal_argument_exception","reason":"IOException while reading synonyms_path_path:  (No such file or directory)"}},"status":400}

My mapping code looks like this and synonyms.txt is within the same folder (same level):

'settings': {
            'analysis': {
                'filter': {
                    'english_stemmer': {
                        'type': 'stemmer',
                        'language': 'english'
                    },
                    'english_possessive_stemmer': {
                        'type': 'stemmer',
                        'language': 'possessive_english'
                    },
                    'my_synonyms': {
                        'type': 'synonym',
                        'synonyms_path' : 'synonyms.txt'                        
                    }
                },
                'analyzer': {
                    'my_analyzer': {
                        'tokenizer': 'standard',
                        'filter': [
                            'english_possessive_stemmer',
                            'lowercase',
                            'my_synonyms',
                            'english_stemmer'
                        ]
                    }
                }
            }
        },
        'mappings' : ...