Index: Lib/trace.py
===================================================================
--- Lib/trace.py	(revision 86303)
+++ Lib/trace.py	(working copy)
@@ -328,10 +328,13 @@
             else:
                 lnotab = {}
 
-            source = linecache.getlines(filename)
+            source = linecache.getlines(filename, sys.modules[modulename].__dict__)
             coverpath = os.path.join(dir, modulename + ".cover")
-            with open(filename, 'rb') as fp:
-                encoding, _ = tokenize.detect_encoding(fp.readline)
+            try:
+                with open(filename, 'rb') as fp:
+                    encoding, _ = tokenize.detect_encoding(fp.readline)
+            except IOError:
+                encoding = None
             n_hits, n_lines = self.write_results_file(coverpath, source,
                                                       lnotab, count, encoding)
             if summary and n_lines:
@@ -416,35 +419,46 @@
     line that contains only a string or a part of a triple-quoted
     string.
     """
+    with open(filename, encoding=encoding) as f:
+        return find_docstrings(f)
+
+def find_docstrings(stream):
     d = {}
     # If the first token is a string, then it's the module docstring.
     # Add this special case so that the test in the loop passes.
     prev_ttype = token.INDENT
-    with open(filename, encoding=encoding) as f:
-        tok = tokenize.generate_tokens(f.readline)
-        for ttype, tstr, start, end, line in tok:
-            if ttype == token.STRING:
-                if prev_ttype == token.INDENT:
-                    sline, scol = start
-                    eline, ecol = end
-                    for i in range(sline, eline + 1):
-                        d[i] = 1
-            prev_ttype = ttype
+    tok = tokenize.generate_tokens(stream.readline)
+    for ttype, tstr, start, end, line in tok:
+        if ttype == token.STRING:
+            if prev_ttype == token.INDENT:
+                sline, scol = start
+                eline, ecol = end
+                for i in range(sline, eline + 1):
+                    d[i] = 1
+        prev_ttype = ttype
     return d
 
 def find_executable_linenos(filename):
     """Return dict where keys are line numbers in the line number table."""
-    try:
-        with io.FileIO(filename, 'r') as file:
-            encoding, lines = tokenize.detect_encoding(file.readline)
-        with open(filename, "r", encoding=encoding) as f:
-            prog = f.read()
-    except IOError as err:
-        print(("Not printing coverage data for %r: %s"
-                              % (filename, err)), file=sys.stderr)
-        return {}
-    code = compile(prog, filename, "exec")
-    strs = find_strings(filename, encoding)
+    modulename = fullmodname(filename)
+    module = sys.modules[modulename]
+    loader = getattr(module, '__loader__', None)
+    if loader:
+        code = loader.get_code(modulename)
+        source = loader.get_source(modulename)
+        strs = find_docstrings(io.StringIO(source))
+    else:
+        try:
+            with io.FileIO(filename, 'r') as file:
+                encoding, lines = tokenize.detect_encoding(file.readline)
+            with open(filename, "r", encoding=encoding) as f:
+                prog = f.read()
+        except IOError as err:
+            print(("Not printing coverage data for %r: %s"
+                                  % (filename, err)), file=sys.stderr)
+            return {}
+        code = compile(prog, filename, "exec")
+        strs = find_strings(filename, encoding)
     return find_lines(code, strs)
 
 class Trace: