fix regular expression in python source `bazelci.py` (#2184)
The code;
```
return re.match("^\${{\s*(\w+)\s*}}$", s)
```
Appears to cause a
[warning](https://buildkite.com/bazel/clion-plugin/builds/24866#01953779-eb82-4f1d-b7bb-ee19e6c4fab3)
in the building of the C-Lion Intelli-J / Bazel plugin;
```
/Users/buildkite/builds/bk-macos-arm64-3wgt/bazel/clion-plugin/bazelci.py:834: SyntaxWarning: invalid escape sequence '\$'
return re.match("^\${{\s*(\w+)\s*}}$", s)
```
It looks like the string should be a raw string. Note that this change
has not been tested.diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 8a6f913..9b1afd3 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -831,7 +831,7 @@
def match_matrix_attr_pattern(s):
- return re.match("^\${{\s*(\w+)\s*}}$", s)
+ return re.match(r"^\${{\s*(\w+)\s*}}$", s)
def get_matrix_attributes(task):
