Bump minimum required version of pandas to 1.5

.github/workflows/pytest-legacy.yml

@@ -25,7 +25,7 @@ jobs:
     - name: Install specific out-dated version of dependencies
       # Update the package requirements when changing minimum dependency versions
       # Please also add a section "Dependency changes" to the release notes
-      run: pip install pandas==1.2.0 numpy==1.19.0 matplotlib==3.5.0 iam-units==2020.4.21 xlrd==2.0 pint==0.13
+      run: pip install pandas==1.5.0 numpy==1.19.0 matplotlib==3.5.0 iam-units==2020.4.21 xlrd==2.0 pint==0.13
 
     - name: Install other dependencies and package
       run: pip install .[tests,optional_plotting,optional_io_formats,tutorials]

RELEASE_NOTES.md

@@ -1,10 +1,12 @@
 # Next Release
 
 The next release must bump the major version number.
-Reactivate tests for Python 3.11 once ixmp4 0.3 is released. 
+Reactivate tests for Python 3.11 once ixmp4 0.3 is released.
 
 ## Dependency changes
 
+Support for Python 3.7-3.9 was removed due to an incompatible dependency.  
+
 PR [#766](https://github.com/IAMconsortium/pyam/pull/766) added the **ixmp4** package
 for better integration with the IIASA scenario database infrastructure.
 

setup.cfg

@@ -34,7 +34,7 @@ install_requires =
     httpx[http2]
     openpyxl
     # remove exception in test_io.py when changing requirement to pandas ≥ 1.5
-    pandas >= 1.2.0
+    pandas >= 1.5.0
     scipy
     pint >= 0.13
     PyYAML

tests/test_io.py

@@ -66,11 +66,7 @@ def test_io_csv_none(test_df_year):
         "model_a,scen_a,World,Primary Energy|Coal,EJ/yr,0.5,3.0\n"
         "model_a,scen_b,World,Primary Energy,EJ/yr,2.0,7.0\n"
     )
-    try:
-        assert test_df_year.to_csv(lineterminator="\n") == exp
-    # special treatment for pandas < 1.5 (used in the legacy tests)
-    except TypeError:
-        assert test_df_year.to_csv(line_terminator="\n") == exp
+    assert test_df_year.to_csv(lineterminator="\n") == exp
 
 
 @pytest.mark.parametrize(