fix: raise chained errors with "from" #998

This makes exceptions report their causes correctly, as "The above exception was
the direct cause of the following exception" instead of "During handling of the
above exception, another exception occurred."

1 files changed, 4 insertions, 4 deletions

diff --git a/coverage/collector.py b/coverage/collector.py
index f9e9d14f..73babf44 100644
--- a/coverage/collector.py
+++ b/coverage/collector.py
@@ -137,12 +137,12 @@ class Collector:
                 self.threading = threading
             else:
                 raise CoverageException(f"Don't understand concurrency={concurrency}")
-        except ImportError:
+        except ImportError as ex:
             raise CoverageException(
                 "Couldn't trace with concurrency={}, the module isn't installed.".format(
                     self.concurrency,
                 )
-            )
+            ) from ex
 
         self.reset()
 
@@ -318,8 +318,8 @@ class Collector:
             (frame, event, arg), lineno = args
             try:
                 fn(frame, event, arg, lineno=lineno)
-            except TypeError:
-                raise Exception("fullcoverage must be run with the C trace function.")
+            except TypeError as ex:
+                raise Exception("fullcoverage must be run with the C trace function.") from ex
 
         # Install our installation tracer in threading, to jump-start other
         # threads.