ext/boto: Could not serialize attribute aws.region to tag when exporting via jaeger

[ThePumpingLemma]

Describe your environment

opentelemetry-api = "=0.9b0"
opentelemetry-ext-boto = "=0.9b0"
opentelemetry-ext-botocore = "=0.9b0"
opentelemetry-ext-dbapi = "=0.9b0"
opentelemetry-ext-jaeger = "=0.9b0"
opentelemetry-ext-psycopg2= "=0.9b0"
opentelemetry-ext-requests = "=0.9b0"
opentelemetry-instrumentation = "=0.9b0"
opentelemetry-sdk = "=0.9b0"
python = "=3.7.4"

Steps to reproduce
Install and enable ext/boto with a jaeger exporter configured. I saw the issue with SES, but I assume other calls have the same problem as well.

What is the expected behavior?
aws.region should be serialized correctly.

What is the actual behavior?
Could not serialize attribute aws.region:('us-east-1',) to tag

Additional context
Not sure how it should be serialized given jaeger doesn't appear to support list types. Probably should be coerced to a string.