Retry WolframScript activation (#677)

## Changes

* Try WolframScript activation up to 3 times before failing.

## Comments

* WolframScript activation [keeps
failing](https://app.circleci.com/pipelines/github/maxitg/SetReplace/2125/workflows/a937820e-d49c-4bfe-b3fe-21fe60fb4aec/jobs/5523)
intermittently because it "could not connect to
https://www.wolframcloud.com/". We cannot avoid doing it, however, we
can decrease the probability of failure by retrying a few times.

## Examples

* Passing wrong `WOLFRAM_ID` and `WOLFRAM_PASSWORD`:

   ```console
   $ export WOLFRAM_ID="test@test.test"
   $ export WOLFRAM_PASSWORD="123"
   $ ./scripts/activateWolframScript.sh 
   Attempt 1...
   Incorrect username or password
   Activation failed on attempt 1. Retrying...
   Attempt 2...
   Incorrect username or password
   Activation failed on attempt 2. Retrying...
   Attempt 3...
   Incorrect username or password
   Activation failed on attempt 3. Retrying...
   Activation failed after 3 attempts.
   $ echo $?
   1
   ```

* [CI
job](https://app.circleci.com/pipelines/github/maxitg/SetReplace/2138/workflows/dd8dffc9-0bcd-4e77-bf8f-be73c98e6018/jobs/5588/parallel-runs/0/steps/0-103)
for this PR:

   ```console
   $ #!/bin/bash -eo pipefail
   $ ./scripts/activateWolframScript.sh
   Attempt 1...
   Success. Saving connection data.
Wolfram Engine activated. See https://www.wolfram.com/wolframscript/ for
more information.
   Activation succeeded on attempt 1.
   ```

Author: maxitg

.circleci/config.yml

@@ -21,9 +21,7 @@ jobs:
 
       - run:
           name: Activate Wolfram Engine
-          command: |
-            wolframscript -authenticate maxitg@icloud.com "${WOLFRAM_PASSWORD}"
-            wolframscript -activate
+          command: ./scripts/activateWolframScript.sh
 
       - run:
           name: Build

scripts/activateWolframScript.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+# Activation is flaky, try up to 3 times.
+n=0
+until [[ ${n} -ge 3 ]]; do
+  ((n++))
+  echo "Attempt ${n}..."
+
+  # Run the activation
+  if wolframscript -authenticate "${WOLFRAM_ID}" "${WOLFRAM_PASSWORD}" && wolframscript -activate; then
+    echo "Activation succeeded on attempt ${n}."
+    break
+  fi
+
+  echo "Activation failed on attempt ${n}. Retrying..."
+  sleep 5
+done
+
+# If after the loop it's still not activated, fail the build
+if [[ ${n} -eq 3 ]]; then
+  echo "Activation failed after 3 attempts."
+  exit 1
+fi