Add setuptools runtime requirement (#2334)

* Add setuptools runtime requirement

The `pkg_resources` module is provided by `setuptools`.
The `setuptools` package is not part of the Python stdlib but is often
available in the system environment as a build-time requirement.

Explicitly listing `setuptools` as a requirement protects
`opentelemetry-python` from breaking with import errors in cases where
`setuptools` is not available system-wide.

This commit pins the version to `setuptools >= 16.0` which is the first
release that includes the required imports (2015).

* Update CHANGELOG

Author: mattoberle

CHANGELOG.md

@@ -18,6 +18,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#2307](https://github.com/open-telemetry/opentelemetry-python/pull/2307))
 - Adding OTEL_LOGS_EXPORTER environment variable
   ([#2320](https://github.com/open-telemetry/opentelemetry-python/pull/2320))
+- Add `setuptools` to `install_requires`
+  ([#2334](https://github.com/open-telemetry/opentelemetry-python/pull/2334))
 - Add otlp entrypoint for log exporter
   ([#2322](https://github.com/open-telemetry/opentelemetry-python/pull/2322))
 

exporter/opentelemetry-exporter-opencensus/setup.cfg

@@ -46,6 +46,7 @@ install_requires =
     opentelemetry-api ~= 1.3
     opentelemetry-sdk ~= 1.3
     protobuf >= 3.13.0
+    setuptools >= 16.0
 
 [options.packages.find]
 where = src

opentelemetry-api/setup.cfg

@@ -45,6 +45,7 @@ include_package_data = True
 install_requires =
     Deprecated >= 1.2.6
     aiocontextvars; python_version<'3.7'
+    setuptools >= 16.0
 
 [options.packages.find]
 where = src

opentelemetry-sdk/setup.cfg

@@ -45,6 +45,7 @@ include_package_data = True
 install_requires =
     opentelemetry-api == 1.8.0
     opentelemetry-semantic-conventions == 0.27b0
+    setuptools >= 16.0
 
 [options.packages.find]
 where = src