#5258/#10642: print fn, line, traceback and continue when .pth file is broken

If a .pth file contained an error, it could cause a traceback in site.py,
terminating its processing.  In 2.7 and 3.2, the interpreter will then not
start.  Previously, a message would print saying to use -v to get the
traceback.  In either case, the traceback generated for a failed .pth file did
not include the .pth filename, making it difficult to debug the problem.  Now
site.py reports not only the .pth filename but also the line number causing the
error, and just skips the remainder of the file.

1 files changed, 19 insertions, 9 deletions

diff --git a/Lib/site.py b/Lib/site.py
index 9d1084a..a2c0bec 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -55,6 +55,7 @@ ImportError exception, it is silently ignored.
 import sys
 import os
 import builtins
+import traceback
 
 # Prefixes for site-packages; add additional prefixes like /usr/local here
 PREFIXES = [sys.prefix, sys.exec_prefix]
@@ -141,17 +142,26 @@ def addpackage(sitedir, name, known_paths):
     except IOError:
         return
     with f:
-        for line in f:
+        for n, line in enumerate(f):
             if line.startswith("#"):
                 continue
-            if line.startswith(("import ", "import\t")):
-                exec(line)
-                continue
-            line = line.rstrip()
-            dir, dircase = makepath(sitedir, line)
-            if not dircase in known_paths and os.path.exists(dir):
-                sys.path.append(dir)
-                known_paths.add(dircase)
+            try:
+                if line.startswith(("import ", "import\t")):
+                    exec(line)
+                    continue
+                line = line.rstrip()
+                dir, dircase = makepath(sitedir, line)
+                if not dircase in known_paths and os.path.exists(dir):
+                    sys.path.append(dir)
+                    known_paths.add(dircase)
+            except Exception as err:
+                print("Error processing line {:d} of {}:\n".format(n+1, fullname),
+                      file=sys.stderr)
+                for record in traceback.format_exception(*sys.exc_info()):
+                    for line in record.splitlines():
+                        print('  '+line, file=sys.stderr)
+                print("\nRemainder of file ignored", file=sys.stderr)
+                break
     if reset:
         known_paths = None
     return known_paths