Revert "scripts: fix pylint in upload_prebuilts.py"

This reverts commit 0cd98cc5f8a49fd809799f2e862c56783b818e5e.

Reason for revert: breaks sdk builder b/235432117

Original change's description:
> scripts: fix pylint in upload_prebuilts.py
>
> BUG=b:234868433
> TEST=cros lint
>
> Change-Id: Ie40140e1ba0dec0deb1896182e5106cf4e4a2f85
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3692196
> Commit-Queue: Sergey Frolov <sfrolov@google.com>
> Reviewed-by: Sloan Johnson <sloanjohnson@google.com>
> Auto-Submit: Sergey Frolov <sfrolov@google.com>
> Tested-by: Sergey Frolov <sfrolov@google.com>

Bug: b:234868433
Change-Id: Id753e7db9b1b8b822470b98bf5eb4c5d54483c88
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3697808
Commit-Queue: Jack Neus <jackneus@google.com>
Reviewed-by: George Engelbrecht <engeg@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
diff --git a/scripts/upload_prebuilts.py b/scripts/upload_prebuilts.py
index 1c12fd3..a30b64f 100644
--- a/scripts/upload_prebuilts.py
+++ b/scripts/upload_prebuilts.py
@@ -108,35 +108,39 @@
   Returns:
     True if changes were made to the file.
   """
-  with open(filename, 'a+') as file_fh:
-    file_lines = []
-    found = False
-    made_changes = False
-    keyval_str = '%(key)s=%(value)s'
-    for line in file_fh:
-      # Strip newlines from end of line. We already add newlines below.
-      line = line.rstrip('\n')
+  if os.path.exists(filename):
+    file_fh = open(filename)
+  else:
+    file_fh = open(filename, 'w+')
+  file_lines = []
+  found = False
+  made_changes = False
+  keyval_str = '%(key)s=%(value)s'
+  for line in file_fh:
+    # Strip newlines from end of line. We already add newlines below.
+    line = line.rstrip('\n')
 
-      if len(line.split('=')) != 2:
-        # Skip any line that doesn't fit key=val.
-        file_lines.append(line)
-        continue
+    if len(line.split('=')) != 2:
+      # Skip any line that doesn't fit key=val.
+      file_lines.append(line)
+      continue
 
-      file_var, file_val = line.split('=')
-      if file_var == key:
-        found = True
-        print('Updating %s=%s to %s="%s"' % (file_var, file_val, key, value))
-        value = '"%s"' % value
-        made_changes |= (file_val != value)
-        file_lines.append(keyval_str % {'key': key, 'value': value})
-      else:
-        file_lines.append(keyval_str % {'key': file_var, 'value': file_val})
-
-    if not found:
+    file_var, file_val = line.split('=')
+    if file_var == key:
+      found = True
+      print('Updating %s=%s to %s="%s"' % (file_var, file_val, key, value))
       value = '"%s"' % value
-      made_changes = True
+      made_changes |= (file_val != value)
       file_lines.append(keyval_str % {'key': key, 'value': value})
+    else:
+      file_lines.append(keyval_str % {'key': file_var, 'value': file_val})
 
+  if not found:
+    value = '"%s"' % value
+    made_changes = True
+    file_lines.append(keyval_str % {'key': key, 'value': value})
+
+  file_fh.close()
   # write out new file
   osutils.WriteFile(filename, '\n'.join(file_lines) + '\n')
   return made_changes