PEP 561 CI x 2.

This commit is the next (and hopefully last) in a commit chain resolving
spurious continuous integration (CI) errors with respect to recently
supported PEP 561 compliance. Specifically, this commit conditionally
installs mypy under tox only when the active Python interpreter is *not*
PyPy, which remains incompatible with mypy. (*Dubious mellifluousness!*)

beartype/_util/py/utilpyinterpreter.py

@@ -4,7 +4,7 @@
 # See "LICENSE" for further details.
 
 '''
-**Beartype Python interpreter utilities.**
+Project-wide **Python interpreter utilities.**
 
 This private submodule is *not* intended for importation by downstream callers.
 '''

beartype/meta.py

@@ -29,14 +29,16 @@
 # installation. This includes all standard Python and package modules but
 # *NOT* third-party dependencies, which if currently uninstalled will only be
 # installed at some later time in the installation.
+#!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 # WARNING: To avoid polluting the public module namespace, external attributes
 # should be locally imported at module scope *ONLY* under alternate private
 # names (e.g., "from argparse import ArgumentParser as _ArgumentParser" rather
 # than merely "from argparse import ArgumentParser").
 #!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
 import sys as _sys
-from typing import Tuple
+from beartype._util.py.utilpyinterpreter import IS_PYPY as _IS_PYPY
+from typing import Tuple as _Tuple
 
 # See the "beartype.cave" submodule for further commentary.
 __all__ = ['STAR_IMPORTS_CONSIDERED_HARMFUL']
@@ -92,7 +94,7 @@
 '''
 
 
-def _convert_version_str_to_tuple(version_str: str) -> Tuple[int, ...]:
+def _convert_version_str_to_tuple(version_str: str) -> _Tuple[int, ...]:
     '''
     Convert the passed human-readable ``.``-delimited version string into a
     machine-readable version tuple of corresponding integers.
@@ -280,12 +282,31 @@ def _convert_version_str_to_tuple(version_str: str) -> Tuple[int, ...]:
 '''
 
 # ....................{ METADATA ~ libs : test            }....................
-LIBS_TESTTIME_MANDATORY_TOX = (
+_LIBS_TESTTIME_MANDATORY_MYPY = (
     # A *VERY* modern version of mypy is recommended. Even fairly recent older
     # versions of mypy are significantly deficient with respect to error
     # reporting to the point of uselessness.
-    'mypy >=0.800',
+    'mypy >=0.800' ,
+) if not _IS_PYPY else ()
+'''
+**Mandatory mypy test-time package dependency** (i.e., dependencies required
+to test this package under :mod:`tox`) as a tuple of :mod:`setuptools`-specific
+requirements strings of the format ``{project_name}
+{comparison1}{version1},...,{comparisonN}{versionN}`` if the active Python
+interpreter is not PyPy *or* the empty tuple otherwise (i.e., if this
+interpreter is PyPy).
+
+See Also
+----------
+:data:`LIBS_RUNTIME_OPTIONAL`
+    Further details.
+https://mypy.readthedocs.io/en/stable/faq.html#does-it-run-on-pypy
+    Official documentation discussing mypy's current incompatibility with PyPy
+    to presumably be fixed at some future point.
+'''
+
 
+LIBS_TESTTIME_MANDATORY_TOX = _LIBS_TESTTIME_MANDATORY_MYPY + (
     # A fairly modern version of pytest is required.
     'pytest >=4.0.0',
 )
@@ -294,6 +315,7 @@ def _convert_version_str_to_tuple(version_str: str) -> Tuple[int, ...]:
 to test this package under :mod:`tox`) as a tuple of :mod:`setuptools`-specific
 requirements strings of the format ``{project_name}
 {comparison1}{version1},...,{comparisonN}{versionN}``.
+
 See Also
 ----------
 :data:`LIBS_RUNTIME_OPTIONAL`

beartype_test/a90_func/pep/test_pep561_static.py

@@ -54,7 +54,6 @@ def test_pep561_mypy() -> None:
     '''
 
     # Defer heavyweight imports.
-    from beartype_test.util.os.command.pytcmdexit import is_success
     from beartype_test.util.path.pytpathproject import get_project_package_dir
     from mypy import api