cython3 need mentioning in the dependencies

When running the compile as in the README, the following failure happens:
```
$ python3 setup.py test
Traceback (most recent call last):
File "/home/hzeller/src/fasm/setup.py", line 28, in
from Cython.Build import cythonize
ModuleNotFoundError: No module named 'Cython'
```

So in the `apt` install line, it would then require `cython3`

Then, the setup test runs but it still fails with some other issue, please advise:
```
File "/home/hzeller/src/fasm/setup.py", line 265, in
setuptools.setup(
File "/usr/lib/python3/dist-packages/setuptools/__init__.py", line 153, in setup
return distutils.core.setup(**attrs)
File "/usr/lib/python3.10/distutils/core.py", line 148, in setup
dist.run_commands()
File "/usr/lib/python3.10/distutils/dist.py", line 966, in run_commands
self.run_command(cmd)
File "/usr/lib/python3.10/distutils/dist.py", line 985, in run_command
cmd_obj.run()
File "/usr/lib/python3/dist-packages/setuptools/command/test.py", line 223, in run
self.run_tests()
File "/usr/lib/python3/dist-packages/setuptools/command/test.py", line 226, in run_tests
test = unittest.main(
File "/usr/lib/python3.10/unittest/main.py", line 100, in __init__
self.parseArgs(argv)
File "/usr/lib/python3.10/unittest/main.py", line 124, in parseArgs
self._do_discovery(argv[2:])
File "/usr/lib/python3.10/unittest/main.py", line 244, in _do_discovery
self.createTests(from_discovery=True, Loader=Loader)
File "/usr/lib/python3.10/unittest/main.py", line 154, in createTests
self.test = loader.discover(self.start, self.pattern, self.top)
File "/usr/lib/python3.10/unittest/loader.py", line 349, in discover
tests = list(self._find_tests(start_dir, pattern))
File "/usr/lib/python3.10/unittest/loader.py", line 405, in _find_tests
tests, should_recurse = self._find_test_path(
File "/usr/lib/python3.10/unittest/loader.py", line 483, in _find_test_path
tests = self.loadTestsFromModule(package, pattern=pattern)
File "/usr/lib/python3/dist-packages/setuptools/command/test.py", line 42, in loadTestsFromModule
tests.append(TestLoader.loadTestsFromModule(self, module))
File "/usr/lib/python3.10/unittest/loader.py", line 121, in loadTestsFromModule
for name in dir(module):
TypeError: 'str' object is not callable
```

Since the stacktrace is a bit hard to read as Python reverses it, here a bit more digestable:
```
TypeError: 'str' object is not callable
/usr/lib/python3.10/unittest/loader.py:121 loadTestsFromModule for name in dir(module):
/usr/lib/python3/dist-packages/setuptools/command/test.py:42 loadTestsFromModule tests.append(TestLoader.loadTestsFromModule(self, module))
/usr/lib/python3.10/unittest/loader.py:483 _find_test_path tests = self.loadTestsFromModule(package, pattern=pattern)
/usr/lib/python3.10/unittest/loader.py:405 _find_tests tests, should_recurse = self._find_test_path(
/usr/lib/python3.10/unittest/loader.py:349 discover tests = list(self._find_tests(start_dir, pattern))
/usr/lib/python3.10/unittest/main.py:154 createTests self.test = loader.discover(self.start, self.pattern, self.top)
/usr/lib/python3.10/unittest/main.py:244 _do_discovery self.createTests(from_discovery=True, Loader=Loader)
/usr/lib/python3.10/unittest/main.py:124 parseArgs self._do_discovery(argv[2:])
/usr/lib/python3.10/unittest/main.py:100 __init__ self.parseArgs(argv)
/usr/lib/python3/dist-packages/setuptools/command/test.py:226 run_tests test = unittest.main(
/usr/lib/python3/dist-packages/setuptools/command/test.py:223 run self.run_tests()
/usr/lib/python3.10/distutils/dist.py:985 run_command cmd_obj.run()
/usr/lib/python3.10/distutils/dist.py:966 run_commands self.run_command(cmd)
/usr/lib/python3.10/distutils/core.py:148 setup dist.run_commands()
/usr/lib/python3/dist-packages/setuptools/__init__.py:153 setup return distutils.core.setup(**attrs)
/home/hzeller/src/fasm/setup.py:265 setuptools.setup(
```

I have no idea what is happening here, does it mean there is an issue in loader.py in the local installation ?