Travis构建中Gcloud报错AttributeError: '_RSAPrivateKey'对象无'sign'属性的求助

Let's walk through practical fixes to resolve this frustrating error—this is a common compatibility issue between cached gcloud SDK versions and cryptography dependencies, especially after interacting with Cloud Shell which may have triggered backend changes.

1. Clear the Google Cloud SDK Cache in Travis #

Travis is likely hanging onto an outdated, incompatible version of the gcloud SDK. Here's how to reset it:

• Head to your project's Travis CI page, navigate to Settings > Caches, and delete the cache entry for $HOME/google-cloud-sdk/.
• Alternatively, temporarily comment out the cache section in your .travis.yml, run one build to let Travis fresh-install everything, then uncomment it afterward.

2. Force a Full Reinstall of the gcloud SDK #

Replace your existing SDK setup steps in before_install to ensure you're getting a clean, up-to-date version:

before_install:
  # ... keep your unrelated steps here
  # Wipe any existing SDK files to start fresh
  - rm -rf $HOME/google-cloud-sdk
  # Install the latest SDK without interactive prompts
  - curl https://sdk.cloud.google.com | bash -s -- --disable-prompts
  # Ensure the SDK is added to your path immediately
  - source $HOME/google-cloud-sdk/path.bash.inc

This eliminates any corrupted or outdated cached files that might be causing conflicts.

3. Lock Cryptography to a gcloud-Compatible Version #

Cryptography versions can clash with gcloud—newer releases sometimes remove methods the SDK depends on. Try installing a stable, compatible version:

before_install:
  # ... other steps
  - pip install cryptography==3.3.2

This version is a proven match for most gcloud SDK builds, and should resolve the missing sign attribute error.

4. Refresh Your Service Account Key #

Even if you didn't modify it, keys can get corrupted during caching or backend updates. Regenerate a new service account key from the Google Cloud Console, replace your travis-credentials.json, re-pack it into credentials.tar.gz, and push the updated file to your repo.

Why This Happened #

The _RSAPrivateKey error almost always comes from a version mismatch between the gcloud SDK and cryptography. When you logged into Cloud Shell, you may have triggered a backend update that changed how key signing works—but Travis was still using its cached, outdated SDK that couldn't handle the new method. Clearing the cache and forcing a fresh install bridges that gap.

内容的提问来源于stack exchange，提问作者Prethia