TypeError: pop() takes no arguments (1 given) with otlp exporter 0.18b0

[markfink-splunk]

Describe your environment
opentelemetry-sdk==1.0.0rc1
opentelemetry-exporter-otlp==1.0.0rc1
opentelemetry-exporter-jaeger==1.0.0rc1
opentelemetry-propagator-b3==1.0.0rc1
opentelemetry-distro==0.18b0
opentelemetry-instrumentation==0.18b0
opentelemetry-instrumentation-grpc==0.18b0
opentelemetry-instrumentation-jinja2==0.18b0

export OTEL_TRACES_EXPORTER="otlp"
export OTEL_EXPORTER_OTLP_INSECURE=true
export OTEL_EXPORTER_OTLP_ENDPOINT="markf-0398:4317"
export OTEL_RESOURCE_ATTRIBUTES="service.name=emailservice, environment=hipster_shop"

Steps to reproduce
I'm using this app, but I don't believe it makes any difference, given the error.
https://github.com/markfink-splunk/microservices-demo/tree/master/src/emailservice

What is the expected behavior?
otlp should initialize and export traces.

What is the actual behavior?
I get this error immediately upon executing "opentelemetry-instrument python email_server.py".

Configuration of configurator failed
Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/opentelemetry/instrumentation/auto_instrumentation/sitecustomize.py", line 74, in _load_configurators
entry_point.load()().configure() # type: ignore
File "/usr/local/lib/python3.7/site-packages/opentelemetry/instrumentation/configurator.py", line 50, in configure
self._configure(**kwargs)
File "/usr/local/lib/python3.7/site-packages/opentelemetry/distro/init.py", line 168, in _configure
_initialize_components()
File "/usr/local/lib/python3.7/site-packages/opentelemetry/distro/init.py", line 159, in _initialize_components
exporter_names = _get_exporter_names()
File "/usr/local/lib/python3.7/site-packages/opentelemetry/distro/init.py", line 73, in _get_exporter_names
exporters.pop(EXPORTER_OTLP)
TypeError: pop() takes no arguments (1 given)
Failed to auto initialize opentelemetry
Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/opentelemetry/instrumentation/auto_instrumentation/sitecustomize.py", line 84, in initialize
_load_configurators()
File "/usr/local/lib/python3.7/site-packages/opentelemetry/instrumentation/auto_instrumentation/sitecustomize.py", line 78, in _load_configurators
raise exc
File "/usr/local/lib/python3.7/site-packages/opentelemetry/instrumentation/auto_instrumentation/sitecustomize.py", line 74, in _load_configurators
entry_point.load()().configure() # type: ignore
File "/usr/local/lib/python3.7/site-packages/opentelemetry/instrumentation/configurator.py", line 50, in configure
self._configure(**kwargs)
File "/usr/local/lib/python3.7/site-packages/opentelemetry/distro/init.py", line 168, in _configure
_initialize_components()
File "/usr/local/lib/python3.7/site-packages/opentelemetry/distro/init.py", line 159, in _initialize_components
exporter_names = _get_exporter_names()
File "/usr/local/lib/python3.7/site-packages/opentelemetry/distro/init.py", line 73, in _get_exporter_names
exporters.pop(EXPORTER_OTLP)
TypeError: pop() takes no arguments (1 given)