Try importing vendored libraries independently

Debian/Ubuntu removes the vendored `yaml` libary, but keeps `lexicon`
and `fluidity`. Trying to import `lexicon` and `yaml` together will fail
in this case: `yaml` is not available from the vendored directory and
`lexicon` from the system.

So try importing vendored libraries independently to allow replacing
them individually.

Author: bdrung

invoke/parser/parser.py

@@ -3,9 +3,11 @@
 
 try:
     from ..vendor.lexicon import Lexicon
-    from ..vendor.fluidity import StateMachine, state, transition
 except ImportError:
     from lexicon import Lexicon  # type: ignore[no-redef]
+try:
+    from ..vendor.fluidity import StateMachine, state, transition
+except ImportError:
     from fluidity import (  # type: ignore[no-redef]
         StateMachine,
         state,

invoke/util.py

@@ -19,9 +19,11 @@
 # more obvious. Requires packagers to leave invoke/vendor/__init__.py alone tho
 try:
     from .vendor.lexicon import Lexicon  # noqa
-    from .vendor import yaml  # noqa
 except ImportError:
     from lexicon import Lexicon  # type: ignore[no-redef] # noqa
+try:
+    from .vendor import yaml  # noqa
+except ImportError:
     import yaml  # type: ignore[no-redef] # noqa