Fix issue with setup requirements not being installed

integrationtests/serpy/requirements_override.nix

@@ -0,0 +1,5 @@
+{ pkgs, python }:
+
+self: super: {
+
+}

integrationtests/test_serpy_0_1_1.py

@@ -0,0 +1,17 @@
+from unittest import TestCase
+
+from .framework import IntegrationTest
+
+
+class SerpyTest(IntegrationTest, TestCase):
+    def name_of_testcase(self):
+        return "serpy"
+
+    def python_version(self):
+        return "3"
+
+    def requirements(self):
+        return ["serpy==0.1.1"]
+
+    def setup_requires(self):
+        return ["six==1.12.0"]

src/pypi2nix/stage1.py

@@ -33,8 +33,19 @@ def build(
         requirements: RequirementSet,
         setup_requirements: Optional[RequirementSet] = None,
     ) -> List[str]:
+        self.ensure_download_directory_exists()
         if setup_requirements is None:
+            self.logger.info("No setup requirements detected")
             setup_requirements = RequirementSet(self.pip.target_platform)
+        else:
+            self.logger.info("Instal setup requirements")
+            setup_requirements = (
+                self.detect_additional_build_dependencies(setup_requirements)
+                + setup_requirements
+            )
+            self.pip.install(
+                setup_requirements, source_directories=[self.download_directory]
+            )
         requirements = requirements + setup_requirements
         detected_requirements = self.detect_additional_build_dependencies(requirements)
         updated_requirements = detected_requirements + requirements