Fix coverage upload

Usage of `coverage` stores data in the internal `.coverage` file that is not supported^1
by codecov.
This results in silently (because we dont use fail option by default) not uploading coverage.

This fixes it by runnin `coverage xml` in coverage_report which outputs a compatible file in `coverage.xml`

1: https://docs.codecov.com/docs/supported-report-formats#non-supported-code-coverage-formats

tasks.py

@@ -24,6 +24,7 @@ def report_cov(ctx: Context, *, html: bool = False):
     """report coverage"""
     ctx.run("coverage combine", warn=True, pty=use_pty)
     ctx.run("coverage report --show-missing", pty=use_pty)
+    ctx.run("coverage xml", pty=use_pty)
     if html:
         ctx.run("coverage html", pty=use_pty)