mercurial/scmutil.py

--- a/mercurial/scmutil.py	Mon Jul 08 13:57:44 2019 -0400
+++ b/mercurial/scmutil.py	Mon Jul 08 14:01:01 2019 -0400
@@ -1541,7 +1541,12 @@
                 pass # we ignore data for nodes that don't exist locally
     finally:
         if proc:
-            proc.communicate()
+            try:
+                proc.communicate()
+            except ValueError:
+                # This happens if we started iterating src and then
+                # get a parse error on a line. It should be safe to ignore.
+                pass
         if src:
             src.close()
     if proc and proc.returncode != 0: