Thanks for the note! I updated the article to reflect the changes in opentelemetry-python 0.12b0. There are a couple of changes that caused the examples to fail:

1. the name of the environment variable used to set the tracer provider was updated from `OPENTELEMETRY_PYTHON_tracer_provider` to `OTEL_PYTHON_TRACER_PROVIDER`

2. The jaeger and flask packages were both renamed. They are now opentelemetry-exporter-jaeger and opentelemetry-instrumentation-flask