handle runtime not being Python in Python BuildPack
because R buildpack subclasses the Python buildpack,
where runtime.txt should be ignored for retrieving the Python version
MODIFY
repo2docker/buildpacks/python/__init__.py
repo2docker/buildpacks/python/__init__.py
@@ -16,7 +16,14 @@ class PythonBuildPack(CondaBuildPack):
with open(self.binder_path('runtime.txt')) as f:
runtime = f.read().strip()
except FileNotFoundError:
- runtime = 'python-' + self.major_pythons['3']
+ runtime = ''
+
+ if not runtime.startswith('python-'):
+ # not a Python runtime (e.g. R, which subclasses this)
+ # use the default Python
+ self._python_version = self.major_pythons['3']
+ return self._python_version
+
py_version_info = runtime.split('-', 1)[1].split('.')
py_version = ''
if len(py_version_info) == 1:

handle runtime not being Python in Python BuildPack

because R buildpack subclasses the Python buildpack,
where runtime.txt should be ignored for retrieving the Python version