cli: revert format() related changes

src/pip/_internal/cli/progress_bars.py

@@ -14,7 +14,7 @@
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
-    from typing import Any, Dict, Iterator, List, Tuple
+    from typing import Any, Dict, List
 
 try:
     from pip._vendor import colorama
@@ -124,7 +124,7 @@ def update(self):
 
 class BlueEmojiBar(IncrementalBar):
 
-    suffix = "{percent:.0f}%"
+    suffix = "%(percent)d%%"
     bar_prefix = " "
     bar_suffix = " "
     phases = (u"\U0001F539", u"\U0001F537", u"\U0001F535")  # type: Any
@@ -203,8 +203,8 @@ class BaseDownloadProgressBar(WindowsMixin, InterruptibleMixin,
                               DownloadProgressMixin):
 
     file = sys.stdout
-    message = "{percent:.0f}%"
-    suffix = "{downloaded} {download_speed} {pretty_eta}"
+    message = "%(percent)d%%"
+    suffix = "%(downloaded)s %(download_speed)s %(pretty_eta)s"
 
 # NOTE: The "type: ignore" comments on the following classes are there to
 #       work around https://github.com/python/typing/issues/241
@@ -238,7 +238,7 @@ class DownloadProgressSpinner(WindowsMixin, InterruptibleMixin,
                               DownloadProgressMixin, Spinner):
 
     file = sys.stdout
-    suffix = "{downloaded} {download_speed}"
+    suffix = "%(downloaded)s %(download_speed)s"
 
     def next_phase(self):  # type: ignore
         if not hasattr(self, "_phaser"):
@@ -247,21 +247,18 @@ def next_phase(self):  # type: ignore
 
     def update(self):
         # type: () -> None
-        vals = dict(self._load_vals(
-            'downloaded', 'download_speed', 'pretty_eta', 'percent'))
-        message = self.message.format(**vals)
+        message = self.message % self
         phase = self.next_phase()
-        suffix = self.suffix.format(**vals)
-        line = " ".join(filter(None, (message, phase, suffix)))
-        self.writeln(line)
+        suffix = self.suffix % self
+        line = ''.join([
+            message,
+            " " if message else "",
+            phase,
+            " " if suffix else "",
+            suffix,
+        ])
 
-    def _load_vals(self, *names):
-        # type: (*str) -> Iterator[Tuple[str, Any]]
-        for name in names:
-            try:
-                yield name, getattr(self, name)
-            except Exception:
-                pass
+        self.writeln(line)
 
 
 BAR_TYPES = {