Catch OSError when source code is not available (#2469)

* Catch OSError when source code is not available

* update changelog with reference to fixed bug

CHANGELOG.md

@@ -36,6 +36,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fixed `!important` not applying to `overflow` https://github.com/Textualize/textual/issues/2420
 - Fixed `!important` not applying to `scrollbar-size` https://github.com/Textualize/textual/issues/2420
 - Fixed `outline-right` not being recognised https://github.com/Textualize/textual/issues/2446
+- Fixed OSError when a file system is not available https://github.com/Textualize/textual/issues/2468
 
 ### Changed
 

src/textual/app.py

@@ -1660,7 +1660,7 @@ class App(Generic[ReturnType], DOMNode):
                     app_css_path = (
                         f"{inspect.getfile(self.__class__)}:{self.__class__.__name__}"
                     )
-                except TypeError:
+                except (TypeError, OSError):
                     app_css_path = f"{self.__class__.__name__}"
                 self.stylesheet.add_source(
                     self.CSS, path=app_css_path, is_default_css=False

src/textual/dom.py

@@ -418,7 +418,7 @@ class DOMNode(MessagePump):
             """Get a path to the DOM Node"""
             try:
                 return f"{getfile(base)}:{base.__name__}"
-            except TypeError:
+            except (TypeError, OSError):
                 return f"{base.__name__}"
 
         for tie_breaker, base in enumerate(self._node_bases):