Fix browser error reporting to find webpack source map files.

When we switched to using webpack, source map files weren't being
logged in the expected place.

zerver/lib/unminify.py

@@ -5,15 +5,15 @@ import os.path
 import sourcemap
 from six.moves import map
 
-from typing import Dict, Text
+from typing import Dict, List, Text
 
 
 class SourceMap(object):
     '''Map (line, column) pairs from generated to source file.'''
 
-    def __init__(self, sourcemap_dir):
-        # type: (Text) -> None
-        self._dir = sourcemap_dir
+    def __init__(self, sourcemap_dirs):
+        # type: (List[Text]) -> None
+        self._dirs = sourcemap_dirs
         self._indices = {}  # type: Dict[Text, sourcemap.SourceMapDecoder]
 
     def _index_for(self, minified_src):
@@ -21,8 +21,12 @@ class SourceMap(object):
         '''Return the source map index for minified_src, loading it if not
            already loaded.'''
         if minified_src not in self._indices:
-            with open(os.path.join(self._dir, minified_src + '.map')) as fp:
-                self._indices[minified_src] = sourcemap.load(fp)
+            for source_dir in self._dirs:
+                filename = os.path.join(source_dir, minified_src + '.map')
+                if os.path.isfile(filename):
+                    with open(filename) as fp:
+                        self._indices[minified_src] = sourcemap.load(fp)
+                        break
 
         return self._indices[minified_src]
 
@@ -31,7 +35,7 @@ class SourceMap(object):
         out = ''  # type: Text
         for ln in stacktrace.splitlines():
             out += ln + '\n'
-            match = re.search(r'/static/min/(.+)(\.[0-9a-f]+)\.js:(\d+):(\d+)', ln)
+            match = re.search(r'/static/(?:webpack-bundles|min)/(.+)(\.[\.0-9a-f]+)\.js:(\d+):(\d+)', ln)
             if match:
                 # Get the appropriate source map for the minified file.
                 minified_src = match.groups()[0] + '.js'