Store DSDL-generated packages in the local directory by default

[pavel-kirienko]

This is a better replacement for #85. It reduces the boilerplate while also avoiding global state.

It used to be:

import sys
import pathlib
import tempfile
import importlib
import pyuavcan
dsdl_generated_dir = pathlib.Path(tempfile.gettempdir(), 'dsdl-for-my-program', f'pyuavcan-v{pyuavcan.__version__}')
dsdl_generated_dir.mkdir(parents=True, exist_ok=True)
sys.path.insert(0, str(dsdl_generated_dir))
try:
    import pyuavcan.application
except (ImportError, AttributeError):
    script_path = os.path.abspath(os.path.dirname(__file__))
    pyuavcan.dsdl.generate_package(
        package_parent_directory=dsdl_generated_dir,
        root_namespace_directory=os.path.join(script_path, '../public_regulated_data_types/uavcan')
    )
    importlib.invalidate_caches()
    import pyuavcan.application

In #85 it was reduced to:

import sys
import pyuavcan
sys.path.insert(0, str(pyuavcan.dsdl.DEFAULT_GENERATED_PACKAGES_DIR))
import pyuavcan.application

The current state is:

import pyuavcan
import pyuavcan.application

[coveralls]

Pull Request Test Coverage Report for Build 694

• 49 of 50 (98.0%) changed or added relevant lines in 19 files are covered.
• 52 unchanged lines in 16 files lost coverage.
• Overall coverage decreased (-6.5%) to 85.879%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyuavcan/dsdl/_composite_object.py	3	4	75.0%
<!--	Total:	49	50	98.0%	-->

Files with Coverage Reduction	New Missed Lines	%
pyuavcan/application/heartbeat_publisher.py	1	84.46%
pyuavcan/presentation/_port/_subscriber.py	1	81.14%
.test_dsdl_generated/uavcan/si/sample/duration/Scalar_1_0.py	1	84.0%
.test_dsdl_generated/uavcan/si/sample/voltage/Scalar_1_0.py	1	84.0%
.test_dsdl_generated/uavcan/si/unit/energy/Scalar_1_0.py	1	84.31%
.test_dsdl_generated/uavcan/si/unit/length/Scalar_1_0.py	1	84.31%
.test_dsdl_generated/uavcan/si/unit/voltage/Scalar_1_0.py	1	84.31%
.test_dsdl_generated/uavcan/si/unit/volumetric_flow_rate/Scalar_1_0.py	1	84.31%
.test_dsdl_generated/uavcan/node/port/GetStatistics_0_1.py	2	91.4%
.test_dsdl_generated/uavcan/node/port/ID_1_0.py	2	89.36%
<!--	Total:	52		-->

Totals
Change from base Build 678:	-6.5%
Covered Lines:	18953
Relevant Lines:	21344

---

💛 - Coveralls