Make keyring optional on ppc64le and s390x

Twine can now be installed on Linux pp64le and s390x without C and Rust
compiler. The `keyring` package has an indirect dependency on `cryptography`
package. Upstream PyCA does not provide wheels for ppc64le and s390x
architecture, because the team has no means to run CI in reasonable
time.

Fixes: 1158
Signed-off-by: Christian Heimes <[email protected]>

.coveragerc

@@ -11,5 +11,8 @@ exclude_lines =
     # Don't complain if non-runnable code isn't run
     if __name__ == .__main__.:
 
+    # exclude typing.TYPE_CHECKING
+    if TYPE_CHECKING:
+
 [html]
 show_contexts = True

pyproject.toml

@@ -36,7 +36,8 @@ dependencies = [
 	"requests-toolbelt >= 0.8.0, != 0.9.0",
 	"urllib3 >= 1.26.0",
 	"importlib-metadata >= 3.6",
-	"keyring >= 15.1",
+	# workaround for missing binaries on these platforms, see #1158
+	"keyring >= 15.1; platform_machine != 'ppc64le' and platform_machine != 's390x'",
 	"rfc3986 >= 1.4.0",
 	"rich >= 12.0.0",
 
@@ -60,6 +61,9 @@ check = "twine.commands.check:main"
 upload = "twine.commands.upload:main"
 register = "twine.commands.register:main"
 
+[project.optional-dependencies]
+keyring = ["keyring >= 15.1"]
+
 [project.scripts]
 twine = "twine.__main__:main"
 

tests/test_auth.py

@@ -1,5 +1,6 @@
 import getpass
 import logging
+import platform
 import re
 
 import pytest
@@ -26,6 +27,15 @@ def get_credential(system, user):
     assert username == "entered user"
 
 
+def test_get_username_keyring_not_installed_defers_to_prompt(
+    monkeypatch, entered_username, config
+):
+    monkeypatch.setattr(auth, "keyring", None)
+
+    username = auth.Resolver(config, auth.CredentialInput()).username
+    assert username == "entered user"
+
+
 def test_get_password_keyring_defers_to_prompt(monkeypatch, entered_password, config):
     class MockKeyring:
         @staticmethod
@@ -38,6 +48,15 @@ def get_password(system, user):
     assert pw == "entered pw"
 
 
+def test_get_password_keyring_not_installed_defers_to_prompt(
+    monkeypatch, entered_password, config
+):
+    monkeypatch.setattr(auth, "keyring", None)
+
+    pw = auth.Resolver(config, auth.CredentialInput("user")).password
+    assert pw == "entered pw"
+
+
 def test_no_password_defers_to_prompt(monkeypatch, entered_password, config):
     config.update(password=None)
     pw = auth.Resolver(config, auth.CredentialInput("user")).password
@@ -272,3 +291,11 @@ def test_warns_for_empty_password(
     assert auth.Resolver(config, auth.CredentialInput()).password == password
 
     assert caplog.messages[0].startswith(warning)
+
+
+@pytest.mark.skipif(
+    platform.machine() in {"ppc64le", "s390x"},
+    reason="keyring module is optional on ppc64le and s390x",
+)
+def test_keyring_module():
+    assert auth.keyring is not None

twine/auth.py

@@ -1,9 +1,17 @@
 import functools
 import getpass
 import logging
-from typing import Callable, Optional, Type, cast
-
-import keyring
+from typing import TYPE_CHECKING, Callable, Optional, Type, cast
+
+# keyring has an indirect dependency on PyCA cryptography, which has no
+# pre-built wheels for ppc64le and s390x, see #1158.
+if TYPE_CHECKING:
+    import keyring
+else:
+    try:
+        import keyring
+    except ModuleNotFoundError:  # pragma: no cover
+        keyring = None
 
 from twine import exceptions
 from twine import utils
@@ -60,6 +68,9 @@ def system(self) -> Optional[str]:
         return self.config["repository"]
 
     def get_username_from_keyring(self) -> Optional[str]:
+        if keyring is None:
+            logger.info("keyring module is not available")
+            return None
         try:
             system = cast(str, self.system)
             logger.info("Querying keyring for username")
@@ -74,6 +85,9 @@ def get_username_from_keyring(self) -> Optional[str]:
         return None
 
     def get_password_from_keyring(self) -> Optional[str]:
+        if keyring is None:
+            logger.info("keyring module is not available")
+            return None
         try:
             system = cast(str, self.system)
             username = cast(str, self.username)