address comments

bazelisk.py

@@ -306,6 +306,8 @@ def download_bazel_into_directory(version, is_commit, directory):
 
     sha256_path = destination_path + ".sha256"
     expected_hash = ""
+    matcher=re.compile(r"(\d*\.\d*(?:\.\d*)?)(rc\d+)?")
+    matched=matcher.match(version)
     if not os.path.exists(sha256_path):
         try:
             download(bazel_url + ".sha256", sha256_path)
@@ -314,21 +316,20 @@ def download_bazel_into_directory(version, is_commit, directory):
                 sys.stderr.write(
                     "The Bazel mirror does not have a checksum file; skipping checksum verification."
                 )
-                if "https://releases.bazel.build" not in bazel_url:
-                    matched=re.match(r"(\d*\.\d*(?:\.\d*)?)(rc\d+)?", version)
-                    if matched:
-                        (version, rc) = matched.groups()
-                        fallback_url="https://releases.bazel.build/{}/{}/{}".format(
-                            version, rc if rc else "release", bazel_filename
-                        )
-                        download(fallback_url+".sha256", sha256_path)
+                if "https://releases.bazel.build" in bazel_url or not matched:
+                    return destination_path
+                if matched:
+                    (version, rc) = matched.groups()
+                    fallback_url="https://releases.bazel.build/{}/{}/{}".format(
+                        version, rc if rc else "release", bazel_filename
+                    )
+                    try:
+                        download("{}.sha256".format(fallback_url), sha256_path)
                         os.remove(destination_path)
                         download(fallback_url,destination_path)
-                        os.chmod(destination_path, 0o755)
-                    else:
+                    except HTTPError:
                         return destination_path
-                else:
-                    return destination_path
+                    os.chmod(destination_path, 0o755)
             raise e
     with open(sha256_path, "r") as sha_file:
         expected_hash = sha_file.read().split()[0]
@@ -339,20 +340,22 @@ def download_bazel_into_directory(version, is_commit, directory):
     actual_hash = sha256_hash.hexdigest()
     if actual_hash != expected_hash:
         os.remove(sha256_path)
+        os.remove(destination_path)
         print(
             "The downloaded Bazel binary is corrupted. Expected SHA-256 {}, got {}. Fallback to default releases.bazel.build url.".format(
                 expected_hash, actual_hash
             )
         )
-        matched=re.match(r"(\d*\.\d*(?:\.\d*)?)(rc\d+)?", version)
         if matched:
             (version, rc) = matched.groups()
             fallback_url="https://releases.bazel.build/{}/{}/{}".format(
                 version, rc if rc else "release", bazel_filename
             )
-            download(fallback_url+".sha256", sha256_path)
-            os.remove(destination_path)
-            download(fallback_url,destination_path)
+            try:
+                download("{}.sha256".format(fallback_url), sha256_path)
+                download(fallback_url,destination_path)
+            except HTTPError:
+                exit(22)
             os.chmod(destination_path, 0o755)
     return destination_path