Android: Fix stack script regex for "debug lines"

Error showed up in bot logs from:
https://ci.chromium.org/ui/p/chromium/builders/ci/android-cronet-asan-arm-rel/56127

and the bug repro's with the sample line from the script:

echo "#00 0x7324d92d /data/app-lib/org.chromium.native_test-1/libbase.cr.so+0x0006992d" | \
    third_party/android_platform/development/scripts/stack.py \
    --output-directory out/Release

Bug: 1274957
Change-Id: I5cfaf0bc08518baf906d2276541ab19656bc972d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3309161
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#947023}
NOKEYCHECK=True
GitOrigin-RevId: 4dec609f1135488f61d403bb8835bf9e00e95753
diff --git a/development/scripts/stack_core.py b/development/scripts/stack_core.py
index bd1a08b..e869a14 100755
--- a/development/scripts/stack_core.py
+++ b/development/scripts/stack_core.py
@@ -78,9 +78,9 @@
 #   #00 0x7324d92d /data/app-lib/org.chromium.native_test-1/libbase.cr.so+0x0006992d
 # This pattern includes the unused named capture groups <symbol_present> and
 # <symbol_name> so that it can interoperate with the |_TRACE_LINE| regex.
-_DEBUG_TRACE_LINE = re.compile('(.*)(?P<frame>\#[0-9]+ 0x[0-9a-f]{8,16}) '
-                               '(?P<lib>[^+]+)\+0x(?P<address>[0-9a-f]{8,16})'
-                               '(?P<symbol_present>)(?P<symbol_name>)')
+_DEBUG_TRACE_LINE = re.compile(r'(.*)#(?P<frame>[0-9]+) 0x[0-9a-f]{8,16} '
+                               r'(?P<lib>[^+]+)\+0x(?P<address>[0-9a-f]{8,16})'
+                               r'(?P<symbol_present>)(?P<symbol_name>)')
 
 # Examples of matched value lines include:
 #   bea4170c  8018e4e9  /data/data/com.my.project/lib/libmyproject.so