message: Follow redundant_pattern_matching clippy lint
  Closes
diff: <p>
  To recognize Docs.rs from <code>build.rs</code> files, you can test for the environment variable <code>DOCS_RS</code>, e.g.:
  {% filter dedent(levels=3) -%}
  - <pre><code class="lang-rust">if let Ok(_) = std::env::var("DOCS_RS") {
  + <pre><code class="lang-rust">if std::env::var("DOCS_RS").is_ok() {
  // ... your code here ...
  }</code></pre>
  {%- endfilter %}
  