Skip pandoc format and tests when pandoc>=2.7.1 is not available

#208

jupytext/formats.py

@@ -16,7 +16,7 @@
 from .metadata_filter import metadata_filter_as_string
 from .stringparser import StringParser
 from .languages import _SCRIPT_EXTENSIONS, _COMMENT_CHARS
-from .pandoc import pandoc_version
+from .pandoc import pandoc_version, is_pandoc_available
 
 
 class JupytextFormatError(ValueError):
@@ -135,20 +135,14 @@ def __init__(self,
             current_version_number='1.1')
     ]
 
-
-def pandoc_format():
-    """Jupytext's format description for Pandoc's Markdown"""
-
-    return NotebookFormatDescription(
+if is_pandoc_available():
+    JUPYTEXT_FORMATS.append(NotebookFormatDescription(
         format_name='pandoc',
         extension='.md',
         header_prefix='',
         cell_reader_class=None,
         cell_exporter_class=None,
-        current_version_number=pandoc_version())
-
-
-JUPYTEXT_FORMATS.append(pandoc_format())
+        current_version_number=pandoc_version()))
 
 NOTEBOOK_EXTENSIONS = list(dict.fromkeys(['.ipynb'] + [fmt.extension for fmt in JUPYTEXT_FORMATS]))
 EXTENSION_PREFIXES = ['.lgt', '.spx', '.pct', '.hyd', '.nb']

jupytext/pandoc.py

@@ -32,6 +32,15 @@ def pandoc(args, filein=None, fileout=None):
     return out.decode('utf-8')
 
 
+def is_pandoc_available():
+    """Is Pandoc>=2.7.1 available?"""
+    try:
+        pandoc_version()
+        return True
+    except (IOError, PandocError):
+        return False
+
+
 def pandoc_version():
     """Pandoc's version number"""
     version = pandoc(u'--version').splitlines()[0].split()[1]

tests/test_mirror.py

@@ -12,7 +12,7 @@
 from jupytext.compare import compare_notebooks, combine_inputs_with_outputs
 from jupytext.formats import long_form_one_format
 from jupytext.paired_paths import full_path
-from .utils import list_notebooks, skip_if_dict_is_not_ordered
+from .utils import list_notebooks, skip_if_dict_is_not_ordered, requires_pandoc
 
 pytestmark = skip_if_dict_is_not_ordered
 
@@ -261,6 +261,7 @@ def test_ipynb_to_md(nb_file):
     assert_conversion_same_as_mirror(nb_file, 'md', 'ipynb_to_md')
 
 
+@requires_pandoc
 @pytest.mark.parametrize('nb_file', list_notebooks('ipynb'))
 def test_ipynb_to_pandoc(nb_file):
     assert_conversion_same_as_mirror(nb_file, 'md:pandoc', 'ipynb_to_pandoc')

tests/test_read_simple_pandoc.py

@@ -1,8 +1,10 @@
 from testfixtures import compare
 from jupytext.compare import compare_notebooks
 import jupytext
+from .utils import requires_pandoc
 
 
+@requires_pandoc
 def test_pandoc_implicit(markdown='''# Lorem ipsum
 
 **Lorem ipsum** dolor sit amet, consectetur adipiscing elit. Nunc luctus
@@ -22,6 +24,7 @@ def test_pandoc_implicit(markdown='''# Lorem ipsum
     compare(markdown2, markdown3)
 
 
+@requires_pandoc
 def test_pandoc_explicit(markdown='''::: {.cell .markdown}
 # Lorem
 

tests/utils.py

@@ -4,6 +4,7 @@
 import pytest
 from jupytext.cli import system
 from jupytext.cell_reader import rst2md
+from jupytext.pandoc import is_pandoc_available
 
 skip_if_dict_is_not_ordered = pytest.mark.skipif(
     sys.version_info < (3, 6),
@@ -21,6 +22,7 @@ def tool_version(tool):
 requires_flake8 = pytest.mark.skipif(not tool_version('flake8'), reason='flake8 not found')
 requires_autopep8 = pytest.mark.skipif(not tool_version('autopep8'), reason='autopep8 not found')
 requires_sphinx_gallery = pytest.mark.skipif(not rst2md, reason='sphinx_gallery not available')
+requires_pandoc = pytest.mark.skipif(not is_pandoc_available(), reason='pandoc>=2.7.1 not available')
 
 
 def list_notebooks(path='ipynb', skip='World'):