fix failing CI tests (#240)

* fix failing CI tests

* install gsl

* add news

Author: Tieqiong

Diff for: .github/workflows/tests-on-pr.yml

@@ -35,8 +35,8 @@ jobs:
       - name: Install diffpy.pdfgui and requirements
         run: |
           conda install --file requirements/test.txt
-          conda install wxpython diffpy.utils matplotlib-base
-          pip install diffpy.pdffit2==1.4.4rc6
+          conda install wxpython diffpy.utils matplotlib-base gsl
+          pip install diffpy.pdffit2==1.4.4rc4
           python -m pip install . --no-deps
 
       - name: Start Xvfb

Diff for: news/ci.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* no news: modification on CI workflow
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>