Show hopefully friendlier messages

Since relative imports don't work with the `import <>` syntax, suggest
importing the names directly. In this cases, the `i.module` is `None`
and the `i.level` has the number of levels down in the relative import,
e.g. `1` means the current directory.

If there's only one name, suggest:

    use 'import module.name' instead of 'from module import name'

This implements the enhancement proposed in sfstpala#1.

flake8_import_style/__init__.py

@@ -5,7 +5,7 @@
 
 __version__ = pkg_resources.get_distribution(__package__).version
 
-I801 = "I801 use 'import {module}' instead of 'from {module} import {names}'"
+I801 = "I801 use 'import {stmt}' instead of 'from {module} import {names}'"
 
 
 class I8(object):
@@ -22,7 +22,21 @@ def run(self):
             if isinstance(i, ast.ImportFrom):
                 if i.module == "__future__":
                     continue
-                message = I801.format(
-                    module=(i.module or "..."),
-                    names=", ".join(i.name for i in i.names))
+                names = ", ".join(i.name for i in i.names)
+                if i.module is None:
+                    # Relative imports don't work with the `import <>` syntax.
+                    message = I801.format(
+                        stmt=names,
+                        module="." * i.level,
+                        names=names)
+                elif len(i.names) == 1:
+                    message = I801.format(
+                        stmt="{0}.{1}".format(i.module, names),
+                        module=i.module,
+                        names=names)
+                else:
+                    message = I801.format(
+                        stmt=i.module,
+                        module=i.module,
+                        names=names)
                 yield (i.lineno, i.col_offset, message, "I801")

flake8_import_style/tests/__init__.py

@@ -21,7 +21,7 @@ def test_run(self):
         self.assertEqual(list(i8.run()), [(
             1,
             0,
-            "I801 use 'import ...' instead of 'from ... import obj'",
+            "I801 use 'import obj' instead of 'from . import obj'",
             "I801",
         )])
 
@@ -30,7 +30,7 @@ def test_run(self):
         self.assertEqual(list(i8.run()), [(
             1,
             0,
-            "I801 use 'import ...' instead of 'from ... import obj'",
+            "I801 use 'import obj' instead of 'from .. import obj'",
             "I801",
         )])
 
@@ -39,7 +39,16 @@ def test_run(self):
         self.assertEqual(list(i8.run()), [(
             1,
             0,
-            "I801 use 'import mod' instead of 'from mod import obj'",
+            "I801 use 'import mod.obj' instead of 'from mod import obj'",
+            "I801",
+        )])
+
+        tree = ast.parse("from mod import obj1, obj2")
+        i8 = flake8_import_style.I8(tree)
+        self.assertEqual(list(i8.run()), [(
+            1,
+            0,
+            "I801 use 'import mod' instead of 'from mod import obj1, obj2'",
             "I801",
         )])