Don't use experimental backend.

Author: domdfcoding

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
-requires = ["repo-helper", "setuptools>=40.6.0", "wheel>=0.34.2"]
-build-backend = "repo_helper.build"
+requires = ["setuptools>=40.6.0", "wheel>=0.34.2"]
+build-backend = "setuptools.build_meta"

repo_helper.yml

@@ -25,8 +25,6 @@ classifiers:
 
 travis_pypi_secure: "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"
 
-use_experimental_backend: true
-
 conda_channels:
  - domdfcoding
  - conda-forge

tox.ini

@@ -72,7 +72,6 @@ deps =
     twine>=3.2.0
     pep517>=0.9.1
     check-wheel-contents>=0.1.0
-    repo_helper
 commands =
     python -m pep517.build --source --binary "{toxinidir}"
     twine check dist/*