Better exception handling in yaml_dumper

File "/home/jylee/work/example/venv/lib/python3.7/site-packages/troposphere/__init__.py", line 762, in to_yaml
long_form=long_form)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/__init__.py", line 71, in to_yaml
return dump_yaml(data, clean_up, long_form)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/__init__.py", line 44, in dump_yaml
default_flow_style=False
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/__init__.py", line 290, in dump
return dump_all([data], stream, Dumper=Dumper, **kwds)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/__init__.py", line 278, in dump_all
dumper.represent(data)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 27, in represent
node = self.represent_data(data)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 48, in represent_data
node = self.yaml_representers[data_types[0]](self, data)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/yaml_dumper.py", line 100, in map_representer
return dumper.represent_mapping(TAG_MAP, value, flow_style=False)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 118, in represent_mapping
node_value = self.represent_data(item_value)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 48, in represent_data
node = self.yaml_representers[data_types[0]](self, data)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/yaml_dumper.py", line 100, in map_representer
return dumper.represent_mapping(TAG_MAP, value, flow_style=False)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 118, in represent_mapping
node_value = self.represent_data(item_value)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 48, in represent_data
node = self.yaml_representers[data_types[0]](self, data)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/yaml_dumper.py", line 100, in map_representer
return dumper.represent_mapping(TAG_MAP, value, flow_style=False)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 118, in represent_mapping
node_value = self.represent_data(item_value)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 48, in represent_data
node = self.yaml_representers[data_types[0]](self, data)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/yaml_dumper.py", line 100, in map_representer
return dumper.represent_mapping(TAG_MAP, value, flow_style=False)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 118, in represent_mapping
node_value = self.represent_data(item_value)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/yaml/representer.py", line 48, in represent_data
node = self.yaml_representers[data_types[0]](self, data)
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/yaml_dumper.py", line 98, in map_representer
return fn_representer(dumper, key[4:], value[key])
File "/home/jylee/work/example/venv/lib/python3.7/site-packages/cfn_flip/yaml_dumper.py", line 73, in fn_representer
value = ".".join(value)
TypeError: sequence item 0: expected str instance, ODict found

fn_representer could have better exception handling to find out what is causing the error.