Install and use toml conditionally on Python2 (#88)

tomli is not available for Python2, so to keep the Python2
compatibility, we need to install and use toml instead.

Use conditional import on ImportError to avoid introducing tox as new
dependency.

As there is difference in the naming of the toml and tomli error
classes, we use generic Exception. More over, we actually want to
fallback to empty config nevertheless what went wrong.

setup.py

@@ -29,7 +29,8 @@ def get_abs_path(pathname):
     install_requires=[
         "flake8 >= 2.0.0",
         "setuptools >= 10.0.0",
-        "tomli>=1.2.1; python_version < '3.11'",
+        "toml >= 0.7.1; python_version < '3.0'",
+        "tomli >= 1.2.1; python_version >= '3.0' and python_version < '3.11'",
     ],
     setup_requires=["pytest-runner"],
     tests_require=["mock", "pytest"],

src/flake8_requirements/checker.py

@@ -12,17 +12,20 @@
 from pkg_resources import parse_requirements
 from pkg_resources import yield_lines
 
-if sys.version_info >= (3, 11):
-    import tomllib
-else:
-    import tomli as tomllib
+try:
+    if sys.version_info >= (3, 11):
+        import tomllib
+    else:
+        import tomli as tomllib
+except ImportError:
+    import toml as tomllib
 
 from .modules import KNOWN_3RD_PARTIES
 from .modules import STDLIB_PY2
 from .modules import STDLIB_PY3
 
 # NOTE: Changing this number will alter package version as well.
-__version__ = "1.7.8"
+__version__ = "1.7.9"
 __license__ = "MIT"
 
 LOG = getLogger('flake8.plugin.requirements')
@@ -557,7 +560,7 @@ def get_pyproject_toml(cls):
         try:
             with open(pyproject_config_path, mode="rb") as f:
                 return tomllib.load(f)
-        except (IOError, tomllib.TOMLDecodeError) as e:
+        except Exception as e:
             LOG.debug("Couldn't load project setup: %s", e)
             return {}