buildPythonPackage: be able to disable package conflict check

doc/languages-frameworks/python.md

@@ -532,6 +532,7 @@ All parameters from `mkDerivation` function are still supported.
 * `makeWrapperArgs`: A list of strings. Arguments to be passed to `makeWrapper`, which wraps generated binaries. By default, the arguments to `makeWrapper` set `PATH` and `PYTHONPATH` environment variables before calling the binary. Additional arguments here can allow a developer to set environment variables which will be available when the binary is run. For example, `makeWrapperArgs = ["--set FOO BAR" "--set BAZ QUX"]`.
 * `installFlags`: A list of strings. Arguments to be passed to `pip install`. To pass options to `python setup.py install`, use `--install-option`. E.g., `installFlags=["--install-option='--cpp_implementation'"].
 * `format`: Format of the source. Options are `setup` for when the source has a `setup.py` and `setuptools` is used to build a wheel, and `wheel` in case the source is already a binary wheel. The default value is `setup`.
+* `catchConflicts` If `true`, abort package build if a package name appears more than once in dependency tree. Default is `true`.
 
 #### `buildPythonApplication` function
 

pkgs/development/python-modules/generic/default.nix

@@ -42,6 +42,9 @@
 # Additional flags to pass to "pip install".
 , installFlags ? []
 
+# Raise an error if two packages are installed with the same name
+, catchConflicts ? true
+
 , format ? "setup"
 
 , ... } @ attrs:
@@ -141,7 +144,7 @@ python.stdenv.mkDerivation (builtins.removeAttrs attrs ["disabled" "doCheck"] //
 
   postFixup = attrs.postFixup or ''
     wrapPythonPrograms
-
+  '' + lib.optionalString catchConflicts ''
     # check if we have two packages with the same name in closure and fail
     # this shouldn't happen, something went wrong with dependencies specs
     ${python.interpreter} ${./catch_conflicts.py}