Flamenco exclusion filter requires BAM 1.1.7; this is now checked

A warning is shown in the GUI when a BAM version that's too old is used
(instead of simply crashing when an exclusion filter was specified).

blender_cloud/flamenco/bam_interface.py

@@ -1,5 +1,6 @@
 """BAM packing interface for Flamenco."""
 
+import functools
 import logging
 from pathlib import Path
 import typing
@@ -14,6 +15,28 @@ class CommandExecutionError(Exception):
     pass
 
 
+if 'bam_supports_exclude_option' in locals():
+    locals()['bam_supports_exclude_option'].cache_clear()
+
+
+@functools.lru_cache(maxsize=1)
+def bam_supports_exclude_option() -> bool:
+    """Returns True if the version of BAM bundled with Blender supports --exclude.
+
+    This feature was added to BAM 1.1.7, so we can do a simple version check.
+    """
+
+    try:
+        import io_blend_utils
+    except ImportError:
+        # If this happens, BAM won't work at all. However, this function can be called from
+        # the GUI; by being a bit careful while importing, we avoid breaking Blender's GUI.
+        log.exception('Error importing io_blend_utils module.')
+        return False
+
+    return io_blend_utils.bl_info['version'] >= (1, 1, 7)
+
+
 async def bam_copy(base_blendfile: Path, target_blendfile: Path,
                    exclusion_filter: str) -> typing.List[Path]:
     """Uses BAM to copy the given file and dependencies to the target blendfile.
@@ -43,7 +66,11 @@ async def bam_copy(base_blendfile: Path, target_blendfile: Path,
     ]
 
     if exclusion_filter:
-        args.extend(['--exclude', exclusion_filter])
+        if bam_supports_exclude_option():
+            args.extend(['--exclude', exclusion_filter])
+        else:
+            log.warning('Your version of Blender does not support the exclusion filter, '
+                        'copying all files.')
 
     cmd_to_log = ' '.join(shlex.quote(s) for s in args)
     log.info('Executing %s', cmd_to_log)