create_package_and_install properly handles when a `specifier` is not set for a targeted package within setup.py
@@ -234,7 +234,7 @@ if __name__ == "__main__":
addition_necessary = False
# ...do we need to install the new version? if the existing specifier matches, we're fine
- if installed_pkgs[req_name] in req_specifier:
+ if req_specifier is not None and installed_pkgs[req_name] in req_specifier:
addition_necessary = False
if addition_necessary:
