## Dependencies with `yield` and `except`

If you catch an exception using `except` in a dependency with `yield` and you don't raise it again (or raise a new exception), FastAPI won't be able to notice there was an exception, the same way that would happen with regular Python:

=== "Python 3.9+"

    ```Python hl_lines="15-16"

And if you update that local FastAPI source code when you run that Python file again, it will use the fresh version of FastAPI you just edited.

That way, you don't have to "install" your local version to be able to test every change.

!!! note "Technical Details"
    This only happens when you install using this included `requirements.txt` instead of running `pip install fastapi` directly.

            // GitHub actions for contributor PRs uses public build scan instance
            // in this case we need to explicitly configure the PTS server
            // Don't move this line into the lambda as it may cause config cache problems
            extensions.findByType<PredictiveTestSelectionExtension>()?.apply {
                this as PredictiveTestSelectionExtensionInternal

    @BeforeEach
    void setUp() throws Exception {
        source = new Source();

        projectArtifact = createArtifactSpec("project", "1.0", null);
    }

    @Test
    @Disabled("works, but we don't fail on cycles presently")
    void testCircularDependencyNotIncludingCurrentProject()
            throws ArtifactResolutionException, InvalidVersionSpecificationException {
        ArtifactSpec a = createArtifactSpec("a", "1.0");

    }

    void calculateNextPermutation() {
      int j = findNextJ();
      if (j == -1) {
        nextPermutation = null;
        return;
      }
      /*
       * requireNonNull is safe because we don't clear nextPermutation until we're done calling this
       * method.
       */
      requireNonNull(nextPermutation);

      int l = findNextL(j);
      Collections.swap(nextPermutation, j, l);

    ) {
      check(!closed) { "closed" }
      checkOffsetAndCount(source.size, 0, byteCount)
      sink.write(source, byteCount)
    }

    override fun flush() {
      if (closed) return // Don't throw; this stream might have been closed on the caller's behalf.
      sink.flush()
    }

    override fun close() {
      if (closed) return
      closed = true
      detachTimeout(timeout)

    <exportedArtifact>org.eclipse.aether:aether-connector-basic</exportedArtifact>

    <!--
      | NOTE: Don't exclude the wagons or any of their dependencies (apart from the wagon API). This would otherwise
      | provoke linkage errors for wagons contributed by build extensions. We also don't need to exclude the wagons
      | from plugins. Plugins that use wagons directly and declare the corresponding dependency will simply use a

We are going to override the internal parts of Peewee that use `threading.local` and replace them with `contextvars`, with the corresponding updates.

This might seem a bit complex (and it actually is), you don't really need to completely understand how it works to use it.

We will create a `PeeweeConnectionState`:

```Python hl_lines="10-19"
{!../../../docs_src/sql_databases_peewee/sql_app/database.py!}
```

  // In the backport, we don't have those cases and thus don't need this suppression.
  // We keep it to minimize diffs.
  @SuppressWarnings("unchecked")
  public static <E> ImmutableSet<E> copyOf(Collection<? extends E> elements) {
    /*
     * TODO(lowasser): consider checking for ImmutableAsList here
     * TODO(lowasser): consider checking for Multiset here
     */

				time.Unix(0, 3).UTC(),
				time.Unix(0, 3).UTC(),
			},
			time.Unix(0, 3).UTC(),
			4,
		},
		{
			// 3. Tests common time obtained when elements have a mixture of
			// sentinel values and don't have read quorum on any of the values.
			[]time.Time{
				time.Unix(0, 3).UTC(),
				time.Unix(0, 3).UTC(),
				time.Unix(0, 2).UTC(),
				time.Unix(0, 1).UTC(),
				time.Unix(0, 3).UTC(),