findmissing: Update supported branches

Replace 5.7 and 5.8 stable branches with 5.10, and add chromeos-5.10.

Unrelated change mandated by repo:
- Handle "Consider explicitly re-raising using the 'from' keyword"

BUG=None
TEST=Run tool and verify that 5.10 is supported

Change-Id: I96bb01549e200b69743a479daa06f01e79b0fefc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2606646
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
diff --git a/contrib/findmissing/common.py b/contrib/findmissing/common.py
index 3beecd8..4ee7633 100755
--- a/contrib/findmissing/common.py
+++ b/contrib/findmissing/common.py
@@ -32,8 +32,8 @@
 CHROMIUM_REVIEW_BASEURL = 'https://chromium-review.googlesource.com/a'
 
 # Order BRANCHES from oldest to newest
-CHROMEOS_BRANCHES = ['4.4', '4.14', '4.19', '5.4']
-STABLE_BRANCHES = ['4.4', '4.9', '4.14', '4.19', '5.4', '5.7', '5.8']
+CHROMEOS_BRANCHES = ['4.4', '4.14', '4.19', '5.4', '5.10']
+STABLE_BRANCHES = ['4.4', '4.9', '4.14', '4.19', '5.4', '5.10']
 
 UPSTREAM_START_BRANCH = 'v%s' % CHROMEOS_BRANCHES[0]
 
@@ -200,4 +200,4 @@
     try:
         return kernel_metadata_lookup[kernel]
     except KeyError as e:
-        raise KeyError('Conditionals should match Kernel Enum types.', e)
+        raise KeyError('Conditionals should match Kernel Enum types.', e) from e