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<settings>
  ...
  <servers>
    ...
    <server>
      <id>sonatype-nexus-snapshots</id>
      <username>your-sonatype-id</username>
      <password>your-sonatype-pwd</password>
    </server>
    <server>
      <id>sonatype-nexus-staging</id>
      <username>your-sonatype-id</username>
      <password>your-sonatyp-pwd</password>
    </server>
    <server>
      <id>github</id>
      <username>your-github-id</username>
      <password>your-github-pwd<token</password>
    </server>
  </servers>
  ...
</settings>

Encrypted passwords work for the plugin that references the sonatype-nexus passwords, but NOT the one that uses github.  To avoid a cryptic error, enter your github password token in plaintext.