chore: Tell why a coverage report can't be parsed (#187)

CHANGES.md

@@ -1,6 +1,7 @@
 # Release Notes
 
 ## Unreleased
+* Improve error message as to why parsing the Cobertura report failed.
 
 ## 3.3.1 (2024-02-17)
 * Fix total stmts, miss and cover values in the coverage report when an ignore

pycobertura/cobertura.py

@@ -54,17 +54,27 @@ def __init__(self, report, filesystem=None):
         source files referenced in the report. Please check the
         `pycobertura.filesystem` module to learn more about filesystems.
         """
+        errors = []
         for load_func in [
             self._load_from_file,
             self._load_from_string,
         ]:
             try:
                 self.xml = load_func(report)
                 break
-            except BaseException:
+            except BaseException as e:
+                errors.append(e)
                 pass
         else:
-            raise self.InvalidCoverageReport("Invalid coverage file: {}".format(report))
+            raise self.InvalidCoverageReport(
+                """\
+Invalid coverage report: {}.
+The following exceptions occurred while attempting to parse the report:
+* While treating the report as a filename: {}.
+* While treating the report as an XML Cobertura string: {}""".format(
+                    report, errors[0], errors[1]
+                )
+            )
 
         self.filesystem = filesystem
         self.report = report