fix mmh3.hash64 unicode exception with python2 (#10685)

* fix `mmh3.hash64` unicode exception with python2 on Windows

Required for #10637

The test suite improvements in that PR which expand Windows test coverage are what surfaced this bug.

* add unicode test case

datadog_checks_base/datadog_checks/base/utils/db/sql.py

@@ -6,6 +6,7 @@
 
 import mmh3
 
+from datadog_checks.base import ensure_bytes
 from datadog_checks.base.utils.serialization import json, sort_keys_kwargs
 
 # Unicode character "Arabic Decimal Separator" (U+066B) is a character which looks like an ascii
@@ -22,7 +23,7 @@ def compute_sql_signature(normalized_query):
         return None
     # Note: please be cautious when changing this function as some features rely on this
     # hash matching the APM resource hash generated on our backend.
-    return format(mmh3.hash64(normalized_query, signed=False)[0], 'x')
+    return format(mmh3.hash64(ensure_bytes(normalized_query), signed=False)[0], 'x')
 
 
 def normalize_query_tag(query):

datadog_checks_base/tests/base/utils/db/test_db_sql.py

@@ -16,6 +16,7 @@ def test_compute_sql_signature(self):
         when changes are made to the hashing algorithm. Changes to the hash can have
         product impact since the backend expects consistency with the APM resource hash.
         """
+        assert '6db2e4f3905c3b5b' == compute_sql_signature('select * from dÒgs')
         assert '11b755a835280e8e' == compute_sql_signature('select * from dogs')
         assert 'd2a193f97126ad67' == compute_sql_signature('update dogs set name = ? where id = ?')