Pyquil

Fixes

- report non-503 http status errors when creating engagements (1479)
- Ensure adding programs doesn't mutate the first (1477)

Features

- gracefully handle error when QPU unavailable for engagement (1457)

Features

- gracefully handle error when QPU unavailable for engagement (1457)

Improvements and Changes

- `QAMExecutionResult` now includes `execution_duration_microseconds`, providing the amount of time
a job held exclusive hardware access. (randall-fulton, 1436)
- Upgrade `qcs-api-client` so that clients can specify a QCS account on their profile, which `qcs-api-client` will in turn use to set `X-QCS-ACCOUNT-{ID/TYPE}` headers on outgoing QCS requests, most notably during engagement creation. (erichulburd, 1439)

- Upgrade `qcs-api-client` to address bug that occurs when the QCS profile and credentials name do not match. (erichulburd, 1442)

- Allow newer versions of `qcs-api-client` (which allows newer versions of `iso8601` and `pyjwt`) to be used. (vtomole, 1449)

Announcements

- `setup.py` has been removed and will no longer be generated as part of the automated release process.

Improvements and Changes

- Function `pyquil.quilatom.substitute()` now supports substitution of classical `MemoryReference`
objects such as `theta[4]` with their parameter values, enabling user-side parameter substitution.
- Versions of `qcs-api-client` up to 0.20.x are now supported.

Bugfixes

- Fix docs typo in `start.rst`, where an extra parentheses was present in a python code block (ThomasMerkh).
- Fixed typo where `scale` was being used as the `phase` in generation of several waveforms.

Improvements and Changes

- Both `get_qc` and `QPU` now accept an `endpoint_id` argument which is used to engage
against a specific QCS [quantum processor endpoint](https://docs.api.qcs.rigetti.com/#tag/endpoints).

Bugfixes

- Allow `np.ndarray` when writing QAM memory. Disallow non-integer and non-float types.
- Fix typo where `qc.compiler.calibration_program` should be `qc.compiler.get_calibration_program()`.
- `DefFrame` string-valued fields that contain JSON strings now round trip to valid Quil and back to
JSON via `DefFrame.out` and `parse`. Quil and JSON both claim `"` as their only string delimiter,
so the JSON `"`s are escaped in the Quil.