importlib.abc.SourceLoader.get_source() was re-raising SyntaxError and

UnicodeDecodeError as ImportError. That was over-reaching the point of
raising ImportError in get_source() (which is to signal the source
code was not found when it should have). Conflating the two exceptions
with ImportError could lead to masking errors with the source which
should be known outside of whether there was an error simply getting
the source to begin with.

Lib/importlib/_bootstrap.py

@@ -959,25 +959,17 @@ class SourceLoader(_LoaderBasics):
 
     def get_source(self, fullname):
         """Concrete implementation of InspectLoader.get_source."""
-        import tokenize
         path = self.get_filename(fullname)
         try:
             source_bytes = self.get_data(path)
         except OSError as exc:
             raise ImportError("source not available through get_data()",
                               name=fullname) from exc
+        import tokenize
         readsource = _io.BytesIO(source_bytes).readline
-        try:
-            encoding = tokenize.detect_encoding(readsource)
-        except SyntaxError as exc:
-            raise ImportError("Failed to detect encoding",
-                              name=fullname) from exc
+        encoding = tokenize.detect_encoding(readsource)
         newline_decoder = _io.IncrementalNewlineDecoder(None, True)
-        try:
-            return newline_decoder.decode(source_bytes.decode(encoding[0]))
-        except UnicodeDecodeError as exc:
-            raise ImportError("Failed to decode source file",
-                              name=fullname) from exc
+        return newline_decoder.decode(source_bytes.decode(encoding[0]))
 
     def source_to_code(self, data, path, *, _optimize=-1):
         """Return the code object compiled from source.