Fixes parse error of CLI output in template pipeline testing which expects '| str |' format.

Moreover, adding a space between a separator and the content makes links more usable when we put links in the table.

PiperOrigin-RevId: 364968402

Author: jiyongjung

tfx/tools/cli/handler/base_handler.py

@@ -191,11 +191,11 @@ def _subprocess_call(self,
   def _format_table(self, header: Collection[Any],
                     data: Collection[Collection[Any]]):
 
-    def _force_strings(items):
-      return [str(item) for item in items]
+    def _format_as_strings(items):
+      return [f' {item} ' for item in items]
 
-    header = _force_strings(header)
-    data = [_force_strings(row) for row in data]
+    header = _format_as_strings(header)
+    data = [_format_as_strings(row) for row in data]
 
     max_widths = [len(s) for s in header]
     for row in data:

tfx/tools/cli/handler/base_handler_test.py

@@ -207,13 +207,13 @@ def testFormatTable(self):
     handler = FakeHandler(flags_dict)
     self.assertEqual(
         textwrap.dedent("""\
-      +===+===+=====+
-      |abc|d  |False|
-      +===+===+=====+
-      |1  |234|None |
-      +---+---+-----+
-      |xxx|   |[]   |
-      +===+===+=====+
+      +=====+=====+=======+
+      | abc | d   | False |
+      +=====+=====+=======+
+      | 1   | 234 | None  |
+      +-----+-----+-------+
+      | xxx |     | []    |
+      +=====+=====+=======+
       """),
         handler._format_table(('abc', 'd', False),
                               [[1, '234', None], ['xxx', '', []]]))